10kw RV build

Christian

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May 6, 2017
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I plan to build a10kw 24v pack for my RV camper, to replace my dying lead-acid system.
Pack is going to be charged by solar and alternator.
I was also thinking about investigating the possibility to be able to plug in to standard J1772 EV charging stations. There seem to be some interesting open source projects out there for doing this.

Since some parts of my truck are in flammable material(wood), i plan to put the pack in a steel enclosure under the truck with venting holes in a safe direction, (i have mig, tig and access to a cnc that can cut metal).
I really want to overkill everything related to safety since i need to feel safe enough to sleep in there.

I dont decided yet if and for witch bms to go for.
My understanding is that imbalance increase while charge/discharge C rating increase. Since everything in my truck is low power, i should be under 0,3C. To not overload my alternator, while driving i was planing to build in a 500w cell balancing hobby-charger.
So my pack would be balance charged on a regular base anyway, plus low C rating, so i might get away without BMS? But in this case i would feel safer if there was some safe guard.. a circuit who disconnect pack if a certain voltage is reached or some of those top balance bleeders if i find reliable ones.
I plan to never charge to 100% to increase circle life.


I welcome any suggestions, specially about things i should do different because my system is going to be exposed to vibrations.
Has anyone ever open one of those MPPsolar units? I wonder if build quality is good enough to withstand vibrations while driving.
 
WOW 10Kw for a RV is massive I'm working towards 1.5kW system right now to replace my 2 Lead Acid Batteries. that I currently have. I'm at about 600W right now (20Ah @ 24V nominal) and Looking to get to about 100Ah Eventually. But I run LED lights in all fixtures and the only other Electrical Loads are the Stereo and Fans for the hot summers..

You'd have to look at what you use on a daily basis and plan your system accordingly.

I generally use about 20 - 25 Ah on the worst kind of days I am only out at camp for 4 days out of the week so that's how long my batts need to last with no recharging (incase of bad weather) so 100Ah would be perfect. Now I have 200W of solar which in ideal weather will keep the batteries full after every day with my usage. I just plan for the worst case.
 
jdeadman said:
WOW 10Kw for a RV is massive ...

It's not clear what Christian means .... I suspect he means a 10KwHr system ,that's a systemthat has a capacity that can deliver 1Kw for 10 hrs , or 2kw for 5 hrs ...

A 10 Kw system is one that can deliver power at the rate of 10Kw , for an unspecified time .

Big Difference!!
 
Ok, I should be more precise, I plan to build a 10kwh batterie pack who can deliver at a maximum 2kwh rate.

I know it might sound excessive, but I dont use my rv just for holiday, i live all year in in it (I do mainly short time seasonal works, staying a few weeks on a job).
I been logging my power use for the last 2 years.
For example i ran a a few times during the winter in the situation, where I had a job to do an my computer, and was runnning 2 computer(with cpu intensive cad software), lights, printer, the whole day, and heater(webasto) and fridge 24/24 during a few days, during bad weather. Of course i ran out of batterie fast(2x150ah lead), and had to let the engine run 2-3 times 15 minutes a day to be able to finish the job on my computer. This was ridiculous, running a 150kw engine to get under 1kw to my batteries, the idling engine was not getting hot enough to have a complete combustion, so i get a lot of carbon deposits in my engine, and of course fuel cost.. and other non sense bla..


The other reason to have a bigger batterie pack is that with lithium ion, life span increase exponentially when charging and discharging partially. Instead of circling between 0 and 100% SOC , have a bigger pack a circle betwen 10 and 90% will (on paper) increase nr of circles from 500 to over 7000. All EV manufactors limit their SOC:
GM 17 to 80% SOC
Nissan and Tesla limit to 90%

So i dont really need 10 kw on a daily bases, the extra power is mainly there to increase life span of the pack and have the extra power on those rare occasions i need it.
 
I've been a full time RVer for many yrs. and have had solar with FLA - flooded lead acid , and run AC , fridge ,furnace and everything else and have never discharged my batteries more that about 40-45% .
And they lasted 12 1/2 yrs. , died early because I had shore power the last 3 yrs. it was running , and let freeze - so cracked batterer cases .
My batteries were Trojan L16 2 pairsin series for 12v & the 2 pair in parallel for capacity to get 750 amp hrs , these were 6v batteries and weighed 135 lbs. before adding electrolyte .
With the cost of lead doubling since I bought those - $650 , now about $1,200 , I. have been looking at options .
One of the issues for me , since I have been staying winter in MN , the lithium need to be warm for charging , so I will probably run a heating duct to battery box .
My inverter is much like the battery system , not a hobby , the inverter is 2500 watts continuous and 4000 surge , also has 100 amp battery charger internal and a transfer switch , will up grade someday to about 4000 watt cont. & 240vacsine wave , the solar is at around 1200-1400 ++ , buying more panels but not using and in storage , so lost count .
 
12years for lead-acid batteries is a lot, mine are 2 years but they were a few times deep-discharged.
I've been also looking at the freezing problem.
Some claim that lithium-ion can be charged in the cold at reduced charging rate: 0,25C at 0C and 0,02C at -30C, but i dont know how reliable those numbers are, or if this just apply to specific cells. Tesla does this by limiting the regenerative breaking at low temperatures.
 
small update:
bms is going to be SBMS40
CellLog with alarm output tripping all DCbreakers
custom CNCed cellhoulders with HRC fuses on each cell
 
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