Lithium battery setup for camper truck

New to renewable energy? Have questions? Here's a great place to ask them and view information about wind and solar power basics.

Lithium battery setup for camper truck

Postby Bris31 » Sat Sep 12, 2015 7:36 pm

My first post and hope I am in right place to ask this question about house battery in a campervan.

I want a 12V 200ah lithium house battery in the campervan as a house battery to be charged both from 12V vehicle alternator - when vehicle is moving and from a 200W solar panel when it is stationary.
Can I connect alternator (90Ah) current directly to MPPT (a Victron 75|50) via a ignition control switch? Solar panel will be also connected to same MPPT but will charge when vehicle is stationary - via above ignition control switch. Lithium will have its own BMS for protecting and managing it.

Thanks in advance.
Bris31
Solar Supporter
Solar Supporter
 
Posts: 3
Joined: Sat Sep 12, 2015 6:41 pm

Re: Lithium battery setup for camper truck

Postby Gordon-Loomberah » Sun Sep 13, 2015 8:48 am

Welcome to the Energy Matters Forums Bris31 :)

There would be no point using a MPPT charge controller to charge the battery from the regulated output of the 12V alternator, as the alternator output voltage is not high enough (I'm assuming a 12V, not 24V, system in the campervan). If you removed the regulator, then yes it would work, so long as you didn't exceed the CC's input current and voltage limits, but then it wouldn't be much good for the Lead-acid starter battery! A PWM type regulator would be much more suitable for that job.

Alternatively, just run the 2 batteries in parallel. However, you don't really want to keep the Lithium battery at the car battery voltage all the time, so you need a automatic or manual (and dont forget!) method of disconnecting the alternator from the battery, once it is charged.

Use the MPPT charge controller only between the PV panel and battery.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5763
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Lithium battery setup for camper truck

Postby Bris31 » Sun Sep 13, 2015 11:29 am

Hi Gordon-Loomberah, thanks for the welcome. :)
And thanks for the explanation.

For my setup, both vehicle and campervan systems are 12V.

Questions (sorry if they sound silly), is every vehicle's alternator is always regulated or how can I test it on my vehicle (mitsubishi canter)? Do I need to disconnect starter lead batteries (x2) to take the measurement? Also do the voltage/current change with the vehicle's speed when alternator is reved up?

So if lithium is being charged directly from the alternator, what is the device which will disconnect it when lithium is fully charged (I will using BMS though)?
Bris31
Solar Supporter
Solar Supporter
 
Posts: 3
Joined: Sat Sep 12, 2015 6:41 pm

Re: Lithium battery setup for camper truck

Postby Gordon-Loomberah » Sun Sep 13, 2015 1:50 pm

Car alternators are always regulated to charge the starting battery in the car, at generally a bit over 14V.

You can see what yours is by putting a multimeter set to read DC voltage across your battery without the motor running, when it will probably be in the mid to high 12s, and after you start it, it will quickly go to the regulated voltage. No need to disconnect anything when checking voltage. Even revving the engine a lot should not cause any increase (< 0.1V) once the battery is charged to the regulated voltage, which happens very quickly if it starts easily. Alternators are "geared up" by 2X or more over the engine speed with a V or toothed belt, so that even at idle they spin fast enough to output a fair proprtion of their rated current at the regulated voltage.
With an engine revved to a few thousand RPM, an alternator without regulation would blow all the light bulbs and damage most electrical devices in the car that weren't saved by blowing fuses, and probably wreck the battery.

You'd generally use a relay or mechanical isolator to disconnect the Lithium battery from the vehicle's charging circuit. 4WD places generally have this sort of gear, but make sure you get a decent quality unit with contacts rated for high current. I once saw one that had some sort of foamy metal (full of air bubbles) in it instead of solid Copper or brass - very light weight, but rubbish for the job. Also very important is the use of sufficiently large diameter Copper cables, otherwise there is the risk of the insulation getting so hot it catches on fire!

You might want to install an accurate digital volt meter to monitor the Lithium battery voltage, as it is best not to keep it at over 14V for extended periods if you want it to last a long time.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5763
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Lithium battery setup for camper truck

Postby Bris31 » Tue Sep 15, 2015 10:53 am

Thanks a lot for the detailed explanation. I am lot wiser now.
Cheers
Bris31
Solar Supporter
Solar Supporter
 
Posts: 3
Joined: Sat Sep 12, 2015 6:41 pm

Re: Lithium battery setup for camper truck

Postby alanporter » Wed Sep 16, 2015 4:54 pm

Hi, re Lithium batteries in Canter,
It is important to use a DC/DC 12 v charger so that your start battery will fully charge your house batteries.
On the market these days are DC/DC chargers that also incorporate a solar charger so you do not have to manually turn on switches.
Two of these are the Redarc BCDC 1225/1240 series including a relay, and the ctek D250dual.
With these you just connect the cables correctly and it all happens automatically.
With both, you must know if your alternator is an older fixed charge unit or a newer variable charge unit. If a newer one, you probably need a connection to ignition.
I am wiring a new Motorhome at the moment with a Redarc 1240 LV to handle a 250AH AGM deep cycle battery plus 290 watts solar.
My only possible problem is your lithium batteries - need to take advice from the supplier if the unit is suitable.
alanporter
Solar Supporter
Solar Supporter
 
Posts: 1
Joined: Wed Sep 16, 2015 4:40 pm

Re: Lithium battery setup for camper truck

Postby davef » Wed Sep 16, 2015 8:54 pm

There is an extremely long thread at http://www.cruisersforum.com/forums/f14/lifepo4-batteries-discussion-thread-for-those-using-them-as-house-banks-65069-312.htmlabout LiFePO4 batteries.
It will take days to read through the thread. There are links to a few sites that try to summarise the important bits. There are also one or more Australian RV websites mentioned.

Seems one of the biggest problems is integrating these batteries into systems using alternators. Other major issues are proper termination of charge, charging disconnection (HVC), load disconnection (LVC), etc.

I have linked to the current last page. If you read through the last few pages you will see quite a lot of discussion re alternators.

Happy reading.
Dave
davef
Solar Evangelist
Solar Evangelist
 
Posts: 91
Joined: Wed Sep 16, 2015 8:40 pm
Location: Christchurch, NZ

Re: Lithium battery setup for camper truck

Postby Tracker » Thu Sep 17, 2015 12:17 pm

..
IF we already have a charge controller for the Solar Panels, AND you want to charge from the car, I wonder if you could compromise and use a Buck-Inverter in the car..

I think you can get them at at least 100W, perhaps 200..

This could feed say 24V to the van, and provided the device was self-limiting (so it does not self destruct), the same charge controller could be used and just switch the input..

Yes - it is only a trickle charger at like 8amps, but even that is not bad when driving along..
and you would likely not get too much more from the alternator, without changing to perhaps a truck alternator, and I doubt that is a simple job in a modern engine.. (no problems with the old HK ;) )

http://www.aliexpress.com/item/12v-to-24v-dc-converter-12A-288W/1770893563.html?spm=2114.031010208.4.1.4Wf4CR&s=p

and here IS one at supposed 280W, that is near 20A charging

12v to 24v dc converter 12A 288W
Specification Full power Synchronous Rectification
Efficient conversion rate > 93%
Working temperature -40 +85
Waterproof Shakeproof
Using thermal silicone sealant(much better than epoxy resin)
Defensive function
Flash input
Output overcurrent
Chip overheating protection
(note: no reverse connect protection/short circuit protection, please carefully wiring, otherwise the power supply can damage
Advice use the less 2~3 A than Max A,The power supply life will be much longer.
Reach about Max A,advise increase the cooling

..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
1.7kW First Solar/Outback Island circuit - Peak Replacement Power
Governments won't save the world :-) They will just TAX it :-(
Tracker
Solar Crusader
Solar Crusader
 
Posts: 5113
Joined: Wed Sep 23, 2009 5:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: Lithium battery setup for camper truck

Postby davef » Thu Sep 17, 2015 2:56 pm

A good suggestion. Gets around the hassle of trying to integrate an alternator into the system.

From my reading one does not want to float LiFePO4 but to completely disconnect the charger from the battery, when charging has reached a certain level.

Perhaps consider using this boost inverter to charge up to 70-80% SOC (or whatever the latest recommendation is) then disconnect until the SOC drops down to whatever the latest recommendation is, ie 50%? Repeat.

I plan to do this with my LiFePO4/solar/microhydro system in 2-3 months.
davef
Solar Evangelist
Solar Evangelist
 
Posts: 91
Joined: Wed Sep 16, 2015 8:40 pm
Location: Christchurch, NZ

Re: Lithium battery setup for camper truck

Postby Gordon-Loomberah » Thu Sep 17, 2015 3:15 pm

davef wrote:From my reading one does not want to float LiFePO4 but to completely disconnect the charger from the battery, when charging has reached a certain level.


If there were going to be no loads on it for some time, then yes that works, but for household applications I don't know of anyone doing that. It is done for EV, EB, RC etc applications though, but they have a completely different mode of use to a household power supply, which is what a camper truck mostly is when in use. If it is going to be unused for an extended period, particularly in hot conditions, then it is best to store it starting from 50 or 60% SOC, with recharging back to that level before it gets too low.

I have my float set to be a very slight net discharge for the rest of the day after I've finished the Absorb stage. If I was going to be cycling between 50 and 80% multiple times per day, I'm sure the battery life would be considerably shortened, due to having 2-3X the number of cycles.

As I have it set up here, the battery is very slightly discharging from where it would sit if the charger was disconnected and no loads were applied, as I've detailed in other threads about Lithium in the forum. The charge controllers only supply what the loads are using, plus make up time lost due to clouds passing over, so I can start the time after sunset (just after 4pm here ATM) with a reasonably high SOC to meet night time loads. Cycling between 50-80% during the day wouldn't work very well at all, as I'd sometimes be starting the overnight discharge with the necessity of running a generator before sunrise. That could well be the case with the camper truck too, especially if you have significant night time loads.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5763
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Next

Return to Q&A - wind and solar power basics

Who is online

Users browsing this forum: No registered users and 1 guest

new solar power specials