DIY lithium battery warmer, Trial and error | EP35 | Ford Transit Campervan Build 

Thank you, I replied to your other comment

Hope it all works out for you and having now had it installed for a year I am happy with the results

Much appreciated!

Cheers. I’ve been happy with the performance. Aye that’s should definitely work with a diy battery too, one of my friends is doing it for their pack. If you are going to stick them directly to the cells maybe still consider some sort of heat sink like my aluminium plate. Unwise you might heat up one particular area most than others.

Glad you it was helpful. although the video is a bit longer as I showed my failures in the first version I quite like the transparency I try and put in my van project videos showing the failures as well as the successes

@@MispronouncedAdventures Nah mate - not long at all, it's perfect - walking through the problem to the solution it probably what lots of us van builders go through - mostly in the middle of the night !

What’s your definition of cold in the context? +5c or -20c And what variation of lithium chemistry or cell type are you using for starters in snowmobiles? ( generally interested, because I didn’t know of many lithium starters. ) Normal LiFePO4 cells can still access decent C rate discharges for normal use below zero. However cranking C rates I’d imagine are massive. Heating the cell via use is a good way to do it.

I think generally when I living in the van full time, the use of the diesel heater will keep the overall temperature in the van above freezing most of the time. But nice to have an automated backup system. Thanks I really enjoy all my smart home tech and automation. Probably going to get a lot of harassment at some point about being in a campervan is being about closer to nature and so on haha. But I lead expedition all over the globe and spend half my year in a tent close to nature, Think I earned myself some smart home luxuries.

Thanks. Yeah my 15w mats definitely looked a bit bigger on the eBay page! . Those hand models must have really small hands! If mine were larger I would of probably done without the heat sink, still playing around with temperature on and offs with the relay, I can probably bring it down a bit lower. But I’ve had them in for about a week now and I’m pretty impressed with the performance.

This heating system is pretty much engine oil sump warmers. A friends of mine who uses Tesla modules for his leisure battery uses a aquarium water heater as those batteries are water cooled / hested

Thanks for watching, glad to found the video helpful. The temperature relays are called a W3230 but “12v temperature relay” should find you other models

Glad you found it useful and are planning on using a similar route. A friend of mine has built my battery warmer designed for his DIY lithium pack and has had similar good results ( main trial and error part is the location of the temperature sensor ) , remember to use a heat sink ( I used the 2mm aluminium plate ) to more evenly spread the heat from the pads. The USB connector was only used on mark one as those heaters were USB powered. Mark two / the final version the heat pads were directly wired to the relay. Heat pads 12v 15W www.ebay.co.uk/itm/15W-12V-5-10cm-Engine-Oil-Tank-Silicone-Heater-Pad-Rubber-Heating-Mat-WarmingKLT-/393018677185?_trksid=p2349624.m46890.l49292 Temperature relay www.ebay.co.uk/itm/Thermostat-Relay-Temperature-Controller-Sensor-Digital-12V-LED-Display-Meter-SPR-/333872298030?_trksid=p2349624.m46890.l49292

Sounds like a good plans and you have sorted your battery heating well

that’s was also part of my thinking as well. As my inverter and solar charger sit in the same cupboard. Hoping when I finally build some cupboard doors heat might be kept in a bit more as well. When in the summer I can disconnect the heat pads and connect a 12v fan to the cupboard vent and change the temperature sensitive relay from heating mode to cooling.

@@MispronouncedAdventures Yeh it would be the best of both worlds, use some 120mm or 140mm noctua PC fans they're almost silent and move enough air and dont use much power so you could just wire a simple switch for them - if it's warm, leave them on!

I had particularly planned on the noctua brand ones, glad to hear you’ve reassured by decision.

@@MispronouncedAdventures The Noctua fans are pricey, but very efficient, and almost silent, as remarked above. Highly recommended.

Half way Down the side of one of the batteries inside the foam jacket. Had to play with it a few time to get a good battery temp but not to be to much direct heat from the heater mat itself

@@MispronouncedAdventures I'll have a play!

Only heats the batteries when the temperature drop of the batteries dropped between 7c and turns off when they reach 9c. This generally only happens on cold nights when the van is unoccupied. And to heat the batteries between those temperatures only takes an hour and 20 minutes usual. Yeah total draw is 3.75amp When they turn on, and since it’s an hour and 20 minutes that’s about 5ah. So just over 1% of the battery banks capacity. The warming system will engage any time the batteries for temp is low enough, for example they might come on at 4 o’clock in the morning and off again at 5:20am but because It did the batteries are in a charging temperature the following morning when the Sun comes up for solar. Or since I have a 30 amp battery to battery charger I just need to turn the engine on for six minutes the next day to recharge the energy used overnight. Couple models on the market now have the same heat pad system built into the batteries internally

Pretty much yes. I think I had to Google the controller part name to find the manual for programming

Generally all DCDC charges are the same input goes to the positive terminal the starter battery or customer connection point if your vehicle has one. Output goes to the positive side of your letter system. Negative connections can vary some DC DDC charges are isolated while some of them are non-isolated and share a common ground. DCDC charges limit the amount of charge current which is important when using lithium. Some of them work in different ways. Some of them need an engine live signal to start was other sense, the vehicles voltage and turn on and off automatically.

The silicon heat pads are aluminium foil taped to the underside of the aluminium plates ( which act as the heat sink to disperse the heat ). The pads them self are solid so not crushable and also extremely flexible. Supported by the aluminium plate above and the 25mm PIR insulation board below.

I appreciate the comment. What’s the issue with the mic? Mainly for reference so I can see what I can fix particularly in post or in camera Is it the peaking at the top end? Or the occasional annoying interference? Which is an annoying issue with this model of Rode video mic

Thanks for the reply!! I think the main issue is clipping at the high end. I'm no mic expert tho

I’m definitely not a mic expert either as you can see or hear to be exact! I play around with some setting so if I can fix it. I suspect it might be the “automatic sensitivity” I’m using in the camera. I’ll have a play

@@MispronouncedAdventures i look forward to hearing improvement in future videos! Are you just using the built in mic in your camera?

No I have use a “Rode Videomic GO” which is an external horseshoe mounted mic. But it is more of a budget member of the Rode mic line up.

Definitely lots of different ways of doing. Best way at the moment I’ve found it to lift the batteries off the ground by 25mm to make an air gap and then use a 1 watt pc fan blow warm air from the diesel heater cabinet under the batteries. If it’s cold enough to get the batteries below zero it’s cold enough my diesel heater is on

@@MispronouncedAdventures I use a hyco 1ft heater to keep van space from freezing when it's not in use

Thin 2 or 3mm closed cell form

I replied to your other comment about using hysteresis

I think I had to use a RU-vid video I found a help program them the instructions can be a bit difficult. I don’t think I set a max temperature I think I set a hysteresis valve. It is the temperature difference between turn on and turn off of the output. If you get the target temp at 10c with a 4c hysteresis. It would turn on a 8c and off at 12c

@@MispronouncedAdventures thank you, I was getting very frustrated.

If they are just Electric-resistance heating elements / pads they have no polarity. So it’s don’t matter. However I would mark up the cables, just so you know which is which so you can wire them up identically

@@MispronouncedAdventures much appreciated , love your vids on your van build not too mention your trip braving the cold through Sweden something for me to aspire to.... Stay safe

The Alexa / echo dot only work with internet connect. whilst the van does have its own 4G router. So most of the time that’s ok. But In the van anything which can use an Alexa, that Is only a secondary way to interact with it. Every primary form of interaction is based of something which will work offline / no WiFi or internet

I have not seen if I’m honest. There is 3mm closed cell foam and duct tape of the jacket before the foam board

If you check out my other videos on my channel you will find a video all about repairing and making an adapter the batteries to use there Communications cable and how to get the software working. :) hope that helps

Sure. I use this one but most “12v temperature relay” should fit that bill for you www.ebay.co.uk/itm/Thermostat-Relay-Temperature-Controller-Sensor-Digital-12V-LED-Display-Meter-SPR-/333872298030?_trksid=p2349624.m46890.l49292

Great, thanks!

Great I had these batteries for the first Arctic trip and in the Roamer ones for the second. However, I had made some modifications pre-1st Arctic trip I found it was extremely effective to lift the batteries off the ground by 25mm to create a air gap so there is no cold bridge between the insulated battery box and the cold floor. I also put a 1watt PC fan to waft warm air from the adjacent diesel heater cabinet into the air gap below. With that upgrade, it was rarely required for the heat pad to turn on. Unless I was not in the vehicle, so the heating was off.

@@MispronouncedAdventures first, thanks for replying. I have a vent going into my garage area from the diesel heater, so when im out in the van its not a problem, but these few days of cold weather being sat on the driveway show that the internal thermometer in my batteries show -1, so i need to sort something out, im glad i asked you now with the 'air gap' tip, im laid up after an operation at the moment, so its killing me not to go out and sort the problem. Your videos are a lifeline at the moment because im just sitting around!!

@youngy7449 i wish you a swift recovery. the air gap or braking the cold bridge is probably the best things for them and helps so much

Currently I have a set temp of 8C with a backlash/Hysteresis of 1C So the heater pads turns on at 7c and off again 9c. I could probably set it a bit lower but so far that’s been working well for me

Oh wow, that is a pretty small range. Do you find that this makes the heaters having to cycle on and off more? I guess the goal is to use the least amount of power while keeping the batteries above freezing. I was planning to do have mine turn on at 5C and off at 10C. You think that is too much?

I guess in my system it has multiple short cycles 7-9c . Whilst 5-10c would be one longer cycle. Remember you don’t need to keep the batteries warm as in hot. You just need to keep them above zero degree, so I only keep them a few degrees above. I could probably lower my 7-9° a bit more. In the case of the heat pads I’m using that doesn’t seem to be any drawbacks of multiple shorter cycles.

10° might be a higher than it needs to be. As quite often during the day at the moment whilst I’m working on the van I don’t often rise above 10° normally. During the night at the minute where it is around about 0 overnight temperatures and I’m not currently in the van ( to the heating is off ) I find the battery warmer switches on twice. Looking back through my Victorn data. I can seeing the battery heater normally turns on for 1:30h to heat the battery from 7 to 9c. So 5.5Ah In total or 3.75amp hour per hour.

@@MispronouncedAdventures ok this is very good information for me thank you. It gives me a good baseline to know where to start my tests. Happy New Year!

I found my heat plate did good job at spreading the heat out from there heat pad. My heat pads were attached to the underside of my spreader plates, which the battery sat on. As for monitoring the heat pads on my initial setup, I placed the temperature relays sensor around midway down central unit. And lucky for me my batteries have a diagnostic cable and four temperature sensors internally so I could log into the batteries and see how accurate the location of the temperature relay sensor was versus the internal battery temperature. It also meant I could check when my initial testing took place at the batteries weren’t getting too hot as well.

@@MispronouncedAdventures that’s great thanks. I’m probably worrying unnecessarily. I’ll put a separate temp sender in between the batteries as I don’t trust the software supplied with the batteries (Lifos brand).

So far brilliant. I do need to still Insulate the top of the batteries as the Victron temperature sensor is mounted to the main POS terminal and exposed to the open air of the van so it’s getting colder and triggering the low temperature cut off, but when I plug the batteries into their diagnostic software I can see the actual internal temperatures of the battery or a few degrees higher. The temperature relay sensor is mounted to the side of the battery inside the insulation and give a more accurate temperature of the bank as a whole.

Awesome, sounds like they’re ready for winter

It’s a dyslexic error haha, I’ll fix that now

All fixed, cheers!

And shouldn’t it say 10 deg c not 0deg c in the description?

I’ve changed it too °C at least I can’t spell it wrong if I just copy and paste the symbol. The operating charge temperature for many lithium cells is around 0°C - 45°C. For testing purposes I was running them a little higher so I can get the relay to trigger. ideally going to set it up so they shouldn’t drop below around 6 or 7 °C

Yes, very much so, but an even more effective solution I found was lifting the batteries off the ground to have an air 25mm underneath and then wafting warmer from the diesel heater area which is nearby underneath them. Well on the Arctic trip last winter. Helps break the cold bridge between the cold floor

@@MispronouncedAdventures I like that idea too. I have a foil backed foam layer already, but it’s not enough, so thought about my diesel heater being in the same compartment and considered taking a small 20mm feed from it and running it across the back of the batteries (using spare heater exhaust tubing insulated to prevent direct contact) and terminating in my fresh water cabinet. I could route below instead…

12v temperature relay would be easy and cheap. I’m struggling to find any 48 V DC options. Does your 48 V system have any stepdown converters in it from 48 down to 12? Might be easier to run a 12 V temperature relay through a step down.

I have a 18-90V DC to DC converter step- down to 12V (buck), so may end up using it, but it also creates heat so I'd have to allow for that. Soo hard to get 48vDC (52VDC) electronic gear. The entire industry is stuck at 12 or 24VDC while everyone is going to 48V or even higher. @@MispronouncedAdventures

It’s been brilliant, I seen it come on now and again if I look at my electrical usage over night. Normally If I’m in the van overnight and the Diesel heater on, they are not needs. But if the van is empty and cold over night in the winter they might turn on for an hour or so.

Glad to hear it! I've built a pair of my own battery banks, and am strongly considering going this route as well.

Mine were as well for which is why I used the plate

@@MispronouncedAdventures I’ll do the same. Currently browsing 1mm aluminium sheets

I found this as a excellent active solution for cold weather heating. However, I think a passive solution which I now have in place as well as the heating pads for the Arctic trip I did last winter was to lift the insulated boxes the lithium battery 25 mm off the ground and put them on tiny stilts, so there is an air gap between cold floor and insulated boxes. Additionally, because my diesel heater is the next cabinet along. I’ve put a small 12v PC fan to waft warm air from the adjacent cabinet underneath the air gap effectively keeping the batteries warm for free. Because if it’s cold enough outside for the batteries to cool down, it’s cold enough for the diesel heater to needing to be overnight. On my Arctic trip ( down to -27c ) with that solution in place, I don’t think the heat pads ever turned on.

@@MispronouncedAdventures thanks for replying so quickly! I'll def get ours raised off the floor that easier enough. I'll make some jackets up like yours and see how I get on. I take it you've not had a problem in hot weather with the jackets on

No problem. Insulation has the same effect in the hot weather. Keep them cooler for longer. Not had any issues with them getting warm. Lifting them off, the ground is definitely one of the best things i did. Swapping 100% contact with a cold surface / the floor to 5% contact makes a huge difference

@@MispronouncedAdventures great insight thanks Alex. As an aside, just got my relay board working on my pi thanks to your latest video on cerbo. Can't afford that at the moment but the pi has served me very well so far. :) Keep on with the videos and adventures. Stay safe.

lto = lithium-titanate batteries? Not sure rhen? Yes, there are plenty of Batteries and lithium chemistries. But those particular chemistries aren’t anywhere near mainstream consumer yet ( in the campervan leisure industry ) but I am aware you can sort your own cells. Only the last few years have battery heaters and low temperature cut offs. become more normal in consumer lithium batteries for campervans. The video is designed for people who didn’t have those features originally It is a rapidly developing industry and lots of new advancements coming, especially with new chemistries. I look forward to the future

The positives of lithium batteries , far out way any cons. the battery warmer comes on for around an hour and 20 minutes consistently at a time ( at 3.75amp. ) on a cold night if the van is left unoccupied and heats the batteries from 7c to 9c. That energy usage is around 1% of the entire pack. Large Lead acid banks in a van builds are just uneconomical weight ( for the same amount of usable energy in lead acid would weight about 150kg whilst this is 55kg ) and power ( the amount of energy lost when charging due it to lead acid being a high resistance battery type ) and money ( 10% of the cycle rate life span of lithium, not not ideal for full timer )

I wholeheartedly disagree with that. I am a full-timer. Lead is more capable. I've documented a lottov of my findings from here: it seems youtube doesn't like the link.. www. fieldlines.com /index.php/ topic,150161.msg 1053973.html#msg1053973 I like your shower implementation that's why I tuned into your channel. I plan to build a conceptually similar system. A battery that burns your van down when the not failsafe safety hardware fails isn't good enough. Worst-case scenario. A battery telling the solar and alternator to throttle/stop producing in the weather you need it the most is pretty ludicrous day to day. Using 30Wh per °C to increase battery temperature is neither efficient nor practical. You'll need 600W of solar to generate that alone with a horizontal mount on a Winter's day. Lead is taking names on that efficiency. Your numbers are incorrect by the way lead is double the weight for the energy density, not one third, it's not high resistance either.

Well you’re more than welcome to disagree. Weight-wise. One of my 95ah lead Acid leisure batteries weight is 25.6kg. With a DoD of 50% ( 47.5ah is usable energy per battery) Each one of my lithium batteries weight 19.5kg which 130ah and a DoD of 80% ( 104ah usable. ( in total for all 3 it’s 58.5kg, apologies for the rough originally stating 55kg ) Let’s do a bit of rounding for math sake. To get 300ah of usable energy from a lead Acid bank would need to be 600ah bank. Given those batteries roughly were 25kg for 100ah ( 50ah Usable ) . You would need 6. That’s 150kg is total, versus 60kg ish for the same usable power in my lithium. And weight is pretty important for build vans. Purpose of the warmer is Keep the battery within safe ( without damaging the cells ) charging parameters, Lithium batteries can be discharged in minus conditions without issue, Just to make sure we are both on the same page this is a warmer load which comes on for an hour maybe once or twice a night and not a continuous load of draw of 3.75amp 24/7? or an hour or two a night maybe ( when the heating isn't on ) As I’m still not sure I quite follow your inefficiency or calculation method, maybe I’ve misunderstood what you said. 3.75amp when the warmer turns on a cold night Normally for around an hour and 20 mins at a time. So 3.75ah per hour of use, so 5ah to heat the batteries for the standard a hour & 20 minutes to get between The temperature controlled relays on and off points 7c & 9c , just over 1% of the banks capacity. Since I’ve got a 30 amp DC to DC Charger the following day I will need to turn the engine on for a total 6 minutes to regain that power used power, as for solar I have 500watts of flat mounted panels. Over the last week I’ve been averaging around 450wh intake per day. So that energy use if the warmer came on once or twice the night before as often regained in the first hour or so ( depending on weather obviously ) As for burning down ones van is pretty hard to achieve thermal run away with a LiFePO4 chemistry as LiFePO4 does not ignite or explode ( unlike lithium polymer which definitely does ). Overcharge, over discharge, short Circuit or physical damage will damage the liFePO4 cells and in cases irreparably, mostly ballooning of the cells in case of LiFePO4. ( unlike LIpo / lithium polymer which can have thermal run away ). As for failsafe that’s why there are multiple. The batteries themselves with built-in BMS’s, and each charger I use particularly use in my vehicle all smart changers are ( multiple charge stages ) and additional failsafes Charging lead acid is less efficient and lithium by far. Especially high rate of charge charging

We might disagree on batteries haha. But as for the shower I will be doing a follow-up video having used it for a while now. But it’s been working great. Only change I’m looking at making a switching to a natural soap as it seems the carbon filters have a easier job at eliminating it. Which seems to be the same case for most other shower builds I’ve seen. What’s your planned heat source for it?

I sent you the link because I've investigated most of what you are saying (sorry it is a bit long-winded) and common knowledge and posted my findings that usually contradict what marketing would like us to believe. You can discharge lead to 80% it costs the same, you can check the graphs on the manufacturer websites. 80% DOD = half as many cycles as 40% DOD. Lead-acid has non-linear efficiency it's actually 100% efficient below 80% SOC and dives after that at higher SOCs. I've not seen a Victron push one passed ~90% SOC so moot point for most. As regards LFP you can get thermal runaway with extreme lithium plating from using high C rates at low temperatures. Incidentally, I can get 100Amp off my alternator to a lead 235Ah battery with a simple contactor and good hearty cable. I can usually exceed those dc-dc jobbers with intelligent cabling. You can actually damage LFP at 15°C if the charge rate is high enough. LFP will last a lot longer if you keep it in the 20% - 80% SOC range but then you get memory effect problems. When you factor this versus £ per kwh lifetime, lead's on top. The simple point is that the batteries in the real world have similar performance and efficiency except one requires a heater, very poor efficiency there and it's way more expensive for the pleasure. The supporting hardware is highly expensive too. Your battery isolator isn't up to the task by the way. Alternator killers those things. They're not switch-disconnect rated and the contacts get pitted and fail over time. Regarding the failsafe nature. Redundancy is not enough. If a part fails the system ought to shut down not limp on at half-mast unattended. If your heaters fail and your Victron not heatsinked temp sensor is giving erroneous readings then what happens? The battery internal BMS is FET based, these fail and continue to operate without notification. When you say charging lead-acid is less efficient by far have you measured this? I have! Add the heater load to the result please.

After testing I found down the side of the battery, about 2/3 of the way down. When I had it too near the bottom it heated up way faster than the battery, Opposite issue near the top. Tested this by connecting the batteries up to their diagnostic software so I can access the four internal temperature sensors on each battery and found those pretty accurate and similar to the location I had put the relay temperature sensor