Available space under 21C seats for electrical

[John in Santa Cruz]

Originally Posted by hugh

They are indeed light, which is one of the reasons I'm hoping to use them! Each of the 304AH cells is around 5.5kg. That's just the cell weight, so bus bars, BMS, box, etc. will add some additional weight. But the battery bank should end up being quite a bit lighter (and cheaper) than using pre-built batteries.
...

FWIW, my 206AH 12V batts are 48 lbs each, so 2 are 96 lbs, and thats 5270 WH total. But the SOK are in nice sturdy metal boxes.

[hugh]

Originally Posted by Centex

My schematic plan is attached FYI (this will be updated to reflect the final as-built configuration). The project is still in progress, all will be documented (with pics) in my modifications thread after everything is completed and functioning.

Have Fun (I am)!

Thanks for the info. Nice diagrams / schematics! Beats the design on the fly, back-of-the-napkin stuff I usually hack together.

I'd be very much looking forward to seeing how it turns out.

[hugh]

Originally Posted by John in Santa Cruz

FWIW, my 206AH 12V batts are 48 lbs each, so 2 are 96 lbs, and thats 5270 WH total. But the SOK are in nice sturdy metal boxes.

Yeah, those SOK's are really nice. Those are the ones where you can open them up to replace cells or the BMS if needed, right?

We'll see how my DIY build goes. I'm a believer that you almost always get what you pay for, so part of me is expecting some unanticipated downside to the DIY approach. (e.g. vibration induced failures, marginal BMS boards, etc.)

[John in Santa Cruz]

Originally Posted by hugh

Yeah, those SOK's are really nice. Those are the ones where you can open them up to replace cells or the BMS if needed, right?

yeah, was a good part of the reason I opted to get them, rather than some of the cheaper alternatives. That and the testing results from the likes of Will Prouse's solar site.

[hugh]

Well, I'm about to finish my build sheet, and thought it would also be a good time to "lock in" the prices on my Lithium batteries. With 2022 Lithium metal supply issues, it seems unlikely that prices will drop any time soon, and in all likelihood, prices will be going up.

I'm taking the DIY route on the battery, and have ordered 16x 230Ah EVE cells, which I'll be assembling into a ~12KWh battery. The pack voltage is still "TBD", but I'm leaning towards a 24 volt system.

The main advantages of a 24 volt system seem to be:

• Wires are ~1/4 the size for same power capacity, so easier to terminate and route
• 24V -> 12V DC to DC step down means constant supply voltage to 12V appliances. Fewer worries about fried 12V boards, flickering lights, etc.
• Significant cost savings on high current components like bus bars, wire, disconnect switches, etc.
• Many more options for solar, inverter, chargers, etc.

The downside of a 24v system seems to be the increase in component count, and minor (<10%) loss of efficiency due to the need to have a step-down converter.

So, any of you with 24 volt systems, feel free to chime in with words of advise, cautions, warnings, or other considerations!

[BobG]

Hugh,
I have 2x 170Ah batteries in series for a 24 volt system. It is about 1/3 the battery capacity of your proposed battery.



I have 1,060 watts of solar flat mounted on the roof. The front and rear panels are 210W each wired in series and the side panels are 4x 160W wired in series. There is continuous shading of panels due to the AC on the roof. The shading pattern changes throughout the day. So far I have been happy with how the 12 volt panels on the sides have been able to keep the voltage high enough to contribute to the 24 volt system.


I have the Victron system including 2 MPPT controllers, smart shunt, MultiPlus inverter/charger, Cerbo and Orion 24-12 volt 70 amp converter. You think the 24-12 volt converter efficiency is greater than 90% but maybe at low currents it is not. I have not found a current vs efficiency curve but suspect at low current the efficiency is less than 90%.



Here are a few comments:
I have the optional 13,500BTU air conditioner and have been running it in the late afternoon and evening when the trailer heats up. I am in Quartzsite, The other day I ran it on low setting from 4:30 when I started cooking dinner until midnight. Usually the on cycle is less than 5 minutes. I use the setting that turns the fan off when the compressor turns off and I use the low setting.



I have an induction hot water kettle that I run an hour or 2 in the mornings for coffee water and maybe some quick breakfast. It uses lots of electricity, about 10% or a little more of the battery.


I run several small items like MiFi, GPS, the Victron equipment, Norcold DC558 refrigerator continuously, and the furnace when it is cold at night. I also run the MaxFan during the day and charge phone, tablet and Kindles. I do not have TV or sound system.


The battery is usually down to 82% by morning and 70% by the time solar starts charging the batteries. I took the batteries down to 40% when I cooked in the trailer and ran the AC to midnight.


This time of year, February in Quartzsite, the solar charges the batteries 100% by 12:30. It barely recovered 100% by evening the time I ran the batteries down to 40%. Sky was clear temperatures in low 80s.



In the Pacific Northwest the solar keeps things gong but if it doesn't get a sunny day within a week I am in trouble.


It takes the inverter/charger almost 3 hours to charge depleted batteries at 24 volts 70 amps.



I don't know what to think about your battery capacity. If you use it regularly like for a big sound system or what ever, then the amount of solar you can place on the roof may not keep up with it. If you reduce the battery by 1/4 then you are looking at going to a 12 volt system. If you cut it in half then you might be balanced better and can add more in the future if you leave room for it.


I am satisfied with going 24 volt instead of 12 volt. Especially with the solar controllers and inverter/charger getting double the bang for the same $. I put everything in the driver side dinette. Maybe I should have put it in the passenger side to better balance the trailer weight.


You will also have to deal with the trailer emergency brake system and power tongue jack if you get one. I went with a mechanical jack and modified it to use a screw driver. I cut off the charging from the tow car since there is solar on the roof.


My trailer is at max weight or a little over. I need to figure out what to leave home. Adding more solar or batteries would be a weight issue for me (21NE).

[hugh]

Originally Posted by BobG

Hugh,
I have 2x 170Ah batteries in series for a 24 volt system. It is about 1/3 the battery capacity of your proposed battery.

I have 1,060 watts of solar flat mounted on the roof. The front and rear panels are 210W each wired in series and the side panels are 4x 160W wired in series. There is continuous shading of panels due to the AC on the roof. The shading pattern changes throughout the day. So far I have been happy with how the 12 volt panels on the sides have been able to keep the voltage high enough to contribute to the 24 volt system.

I have the Victron system including 2 MPPT controllers, smart shunt, MultiPlus inverter/charger, Cerbo and Orion 24-12 volt 70 amp converter. You think the 24-12 volt converter efficiency is greater than 90% but maybe at low currents it is not. I have not found a current vs efficiency curve but suspect at low current the efficiency is less than 90%.


Here are a few comments:
I have the optional 13,500BTU air conditioner and have been running it in the late afternoon and evening when the trailer heats up. I am in Quartzsite, The other day I ran it on low setting from 4:30 when I started cooking dinner until midnight. Usually the on cycle is less than 5 minutes. I use the setting that turns the fan off when the compressor turns off and I use the low setting.

I have an induction hot water kettle that I run an hour or 2 in the mornings for coffee water and maybe some quick breakfast. It uses lots of electricity, about 10% or a little more of the battery.

I run several small items like MiFi, GPS, the Victron equipment, Norcold DC558 refrigerator continuously, and the furnace when it is cold at night. I also run the MaxFan during the day and charge phone, tablet and Kindles. I do not have TV or sound system.

The battery is usually down to 82% by morning and 70% by the time solar starts charging the batteries. I took the batteries down to 40% when I cooked in the trailer and ran the AC to midnight.

This time of year, February in Quartzsite, the solar charges the batteries 100% by 12:30. It barely recovered 100% by evening the time I ran the batteries down to 40%. Sky was clear temperatures in low 80s.

In the Pacific Northwest the solar keeps things gong but if it doesn't get a sunny day within a week I am in trouble.


It takes the inverter/charger almost 3 hours to charge depleted batteries at 24 volts 70 amps.

I don't know what to think about your battery capacity. If you use it regularly like for a big sound system or what ever, then the amount of solar you can place on the roof may not keep up with it. If you reduce the battery by 1/4 then you are looking at going to a 12 volt system. If you cut it in half then you might be balanced better and can add more in the future if you leave room for it.

I am satisfied with going 24 volt instead of 12 volt. Especially with the solar controllers and inverter/charger getting double the bang for the same $. I put everything in the driver side dinette. Maybe I should have put it in the passenger side to better balance the trailer weight.

You will also have to deal with the trailer emergency brake system and power tongue jack if you get one. I went with a mechanical jack and modified it to use a screw driver. I cut off the charging from the tow car since there is solar on the roof.

My trailer is at max weight or a little over. I need to figure out what to leave home. Adding more solar or batteries would be a weight issue for me (21NE).

Thank Bob.


FWIW, I'm sizing the battery to be able to run AC in the evening / night without having to rely on a generator. I'm also planning on using electricity for some cooking needs (convection oven, coffee maker), maybe even a "boost" for the hot water heater if needed.



Here in the mid-Atlantic region, I don't think solar is going to be as useful as a main power source. Many of the camping areas we visit are tree shaded, and we get a fair amount of cloudy weather in the mid-Atlantic. I'm viewing solar as a way to charge between trips, and top-up during towing.



I was considering a smaller battery, but the at $0.15/Wh for the DIY batteries, I can afford to hedge my bets a little and go with the larger battery. I would definitely not be doing that if I was installing the same capacity in BattleBorn's.



The total weight of the LifePO4 cells is in the ball park the 6-volt lead acid batteries that escape installs. I may split the cells into a permanent and removable module, so I can optimize weight on a per-trip basis.



What did you end up doing for your emergency brake? My initial inclination is to use a DC-DC converter, possibly independent from the converter for the other loads.

[BobG]

The emergency break system is supposed to be on a non switched circuit so I wired it directly to the 24 volt busbar prior to the battery switch. I installed a $15 24-12 dc converter and an inline fuse at the busbar. I don't know if the fuse is the proper way to do this or if a thermal breaker would be better but I didn't want to have an unfused wire. The emergency brake circuit is easy enough to test by pulling the pin to see if the fuse is good when hooking up.

[John in Santa Cruz]

Originally Posted by hugh

...I was considering a smaller battery, but the at $0.15/Wh for the DIY batterie...

FWIW, my off the shelf metal cased 12V 206AH batts were $0.19 or $0.20/WH delivered, with a 7 year warranty.


5270 watt*hours, from 2 x SOK 12V 206AH batteries, $2100.

[hugh]

Originally Posted by John in Santa Cruz

FWIW, my off the shelf metal cased 12V 206AH batts were $0.19 or $0.20/WH delivered, with a 7 year warranty.

5270 watt*hours, from 2 x SOK 12V 206AH batteries, $2100.

i was thinking "Holy Moly, that's a good price for the SOK's!", but looking at the pricing again, aren't they actually closer to $0.40/WH?


$2100.00 / 5270 Wh ~= $0.39 / 1Wh ?

[hugh]

Originally Posted by BobG

The emergency break system is supposed to be on a non switched circuit so I wired it directly to the 24 volt busbar prior to the battery switch. I installed a $15 24-12 dc converter and an inline fuse at the busbar. I don't know if the fuse is the proper way to do this or if a thermal breaker would be better but I didn't want to have an unfused wire. The emergency brake circuit is easy enough to test by pulling the pin to see if the fuse is good when hooking up.

Ok, good to know that's your approach. It seems safer than installing a 12v battery just for the emergency brake, as a marginal battery would be difficult to detect by the pin-pull test.

[John in Santa Cruz]

Originally Posted by hugh

i was thinking "Holy Moly, that's a good price for the SOK's!", but looking at the pricing again, aren't they actually closer to $0.40/WH?


$2100.00 / 5270 Wh ~= $0.39 / 1Wh ?

oh geez, did I slip that one? k, yer probably right there.

I'm still quite happy with the SOKs, I think they are built better than anything I would have cobbled together.

re; ebrake circuit. I tested my dual axle brakes the other night on its new wiring, and saw about 15-18 amps from the brakes. I ran a new 10 AWG wire from the back up to the front junction box, powered off the main +12V bus bar (100A fuse on each battery, nothing else in the middle), through one of the original 30A thermal breakers, to the breakaway switch power. you should use a thermal breaker as if you were to blow a regular fuse, you wouldn't even notice if you didn't explicitly check, and could be driving for months with no e-brake power. a thermal breaker will recover from a temporary short

I used the other 30A thermal breaker on the original power wire from the tow vehicle that now goes into the Orion 12/12-18 I used as the LFP charging from tow vehicle power.

I saw no point in fusing the output of the Orion (or the MPPT Smart-Solar) as they are current limited and short proof. The batteries themselves each have a 100A ANL fuse, thats to handle the worst case arc weld grade short on the main AWG 4 wiring.

[hugh]

Originally Posted by John in Santa Cruz

oh geez, did I slip that one? k, yer probably right there.

I'm still quite happy with the SOKs, I think they are built better than anything I would have cobbled together.

re; ebrake circuit. I tested my dual axle brakes the other night on its new wiring, and saw about 15-18 amps from the brakes. I ran a new 10 AWG wire from the back up to the front junction box, powered off the main +12V bus bar (100A fuse on each battery, nothing else in the middle), through one of the original 30A thermal breakers, to the breakaway switch power. you should use a thermal breaker as if you were to blow a regular fuse, you wouldn't even notice if you didn't explicitly check, and could be driving for months with no e-brake power. a thermal breaker will recover from a temporary short

I used the other 30A thermal breaker on the original power wire from the tow vehicle that now goes into the Orion 12/12-18 I used as the LFP charging from tow vehicle power.

I saw no point in fusing the output of the Orion (or the MPPT Smart-Solar) as they are current limited and short proof. The batteries themselves each have a 100A ANL fuse, thats to handle the worst case arc weld grade short on the main AWG 4 wiring.

Yep, those SOK's are a great option, and still half the price of the BattleBorns. The longevity / reliability of my DIY build is much less certain, so I'm taking a bit of a gamble.



Good suggestion on the breaker. I'll definitely incorporate an auto-reset on that circuit.

[BobG]

Yes, I can see how a thermal breaker would be better for the emergency brakes circuit. I will change out the fuse to a breaker next summer when I am home.