Lithium - Drop in replacement?

[arthur49]

I find some of the marketing confusing!

Looking at one particular lithium brand, the max continuous charge current is 100A. The BMS will ensure that will not be exceeded but the cautious me would want to present the battery with ideal charge conditions, with the BMS being a fall-back safety feature.

Lithium as I understand it will accept as much current as you can throw at it, so the example above will accept 100A.

But the power cabling, split charge relay (Tyco) in my van is rated at max 70A, fused sensibly at 50A.

So what prevents the lithium drawing 100A charge whilst driving, if there is no B2B/device to keep the current to a safe limit ie max 50A in my van?

Without some charge control before the BMS, the cables, fuses, split charge relay (and alternator?) are operating well above their safe limit?

(In my last van the Sargent Control Unit and cabling was rated at 25A max)

 

[nabsim]

If your alternator delivers more than the cable is fused for it should blow the fuse. Victron did a video about alternator damage which I have heard is informative but not watched myself

 

[Lenny HB]

Regardless of suppliers saying "a drop in replacement" it's always best to fit it properly with a B2B, solar & mains chargers with the correct profile for Lithium. Doing it properly you will get the best from them & longest life.

 

[arthur49]

Regardless of suppliers saying "a drop in replacement" it's always best to fit it properly with a B2B, solar & mains chargers with the correct profile for Lithium. Doing it properly you will get the best from them & longest life.

That is precisely what I did. I went for 2 x Sterling 100Ah, Votronic 50A B2B etc.
And I will always be wary of a supplier who says "drop in replacement" unless they explain clearly how/why that is the case

 

[RowleyBirkinQC]

We have a Sterling 120Ah lithium, Sterling 60A B2B with lithium profile, Victron MPPT solar controller with lithium profile & Victron smartshunt (or something like that).

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[funflair]

If your alternator delivers more than the cable is fused for it should blow the fuse. Victron did a video about alternator damage which I have heard is informative but not watched myself

I think that video is quite confusing (maybe that's the way they want it) as they seem to neglect to take into account that under normal conditions the alternator will be geared up from engine crank speed by the pulley sizes.

 

[arthur49]

I think that video is quite confusing (maybe that's the way they want it) as they seem to neglect to take into account that under normal conditions the alternator will be geared up from engine crank speed by the pulley sizes.

Charles Sterling did an alternator bench test as well but I can't speak for or against the technical correctness

 

[Waveski]

I’m also looking at installing a 200amp lithium battery and I’m also very confused, my electrical knowledge is limited. Has anyone measured, or has experience of the max charge current from a “standard” Fiat alternator/starter battery to a lithium battery via 16 mm2 cable say 1m long ? I’m aware that some canal boaters use extra long cables to provide resistance to control the max output from the alternator? Some lithium battery suppliers say that a B2b is only required if you have a smart alternator. What restricts the charge to a lead acid battery? Can anyone make sense of all this for a layman?

 

[arthur49]

I’m also looking at installing a 200amp lithium battery and I’m also very confused, my electrical knowledge is limited. Has anyone measured, or has experience of the max charge current from a “standard” Fiat alternator/starter battery to a lithium battery via 16 mm2 cable say 1m long ? I’m aware that some canal boaters use extra long cables to provide resistance to control the max output from the alternator? Some lithium battery suppliers say that a B2b is only required if you have a smart alternator. What restricts the charge to a lead acid battery? Can anyone make sense of all this for a layman?

Can't answer your questions directly but as you say your electrical knowledge is limited I would say get an expert to install if you go ahead.
1. My base is a 2019 Renault Master. The (smart) alternator max output is 180A but Renault advise max amps taken by conversion should be 37A. They do not say if this 37A includes or excludes the 15A approx taken by a 3 way fridge whilst driving. Fiat may be different but I have read somewhere that good practice suggests the max draw from alternator on any base vehicle should be 50A
2. Extra long cables to increase resistance and reduce current is a bodge!
3. B2B is required for smart alternators because the voltage generated can swing between over 15v and under 12v - that is not good for any battery type.
4. In my view a B2B is also required for standard alternators unless any supplier advocating "drop in replacement for lead acid" can persuade me that there is some means of controlling voltage and current to lithium batteries - see Charles Sterling's video above.

 

[Waveski]

Thanks @artthur49. That’s the best simple explanation I’ve yet come across. I’m certainly not competent enough in this area to do the job myself but I do need to understand what is needed so I can sort out the installation experts from some of the others! I would still like to have some data from those that have taken the option of a drop in lithium and any resulting problems. My current thinking is that a B2B is definitely required.

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[nabsim]

Thanks @artthur49. That’s the best simple explanation I’ve yet come across. I’m certainly not competent enough in this area to do the job myself but I do need to understand what is needed so I can sort out the installation experts from some of the others! I would still like to have some data from those that have taken the option of a drop in lithium and any resulting problems. My current thinking is that a B2B is definitely required.

It depends on how you use your vehicle and is really specific to each person. A lot of the ‘drop in’ Lifepo4 I have seen, according to the manufacturers, will work with gel battery settings. If all your charge sources have a gel setting (or of course lithium) then you could have a drop in option.
This doesn’t mean you will be giving or getting the best out of them but does mean some vehicles can drop in replacements.
Check the spec for whatever battery’s you are thinking of and check settings of all charge sources

 

[Lenny HB]

It depends on how you use your vehicle and is really specific to each person. A lot of the ‘drop in’ Lifepo4 I have seen, according to the manufacturers, will work with gel battery settings. If all your charge sources have a gel setting (or of course lithium) then you could have a drop in option.
This doesn’t mean you will be giving or getting the best out of them but does mean some vehicles can drop in replacements.
Check the spec for whatever battery’s you are thinking of and check settings of all charge sources

The problem with the Gel setting is the 16 hour absorption phase that a lot of chargers have is not good for Lithium.

 

[nabsim]

The problem with the Gel setting is the 16 hour absorption phase that a lot of chargers have is not good for Lithium.

Exactly why I said you won’t be giving or getting the best. Personally I would make sure charge sources have correct settings but I think the gel setting option is where the manufacturers/suppliers are getting the drop in bit from.
I know I used gel setting on my mains chargers until I got the cash to uprated that bit but I managed when the chargers ran. I normally only use mains in poor weather/winter from my genny to top up the battery bank so was easy for me. My other sources already had correct settings for Lifepo4. I think it is if someone thinks they can have a drop in and forget option it’s a problem

 

[the1andonly]

A popular topic so some of my ramblings from the past
Having seen the ridiculously thin cables and cheap pwm controller from my dealer install i slowly upgraded things before my 2 banners were no longer for this world. Started with wiring and chosing a votronics mppt controller with future profing in mind thinking of gel at the time. So up went my 100w panel with the 120w already up there. Bit more time upgoes another 330w (£130) so now add another votronics controller. Batteries die just about to concider 3 gel then seen a post here lithium 100ah ebay less than £500 with bt bms. Quick purchase of b2b before battery turns up.
So would have been a simple drop in if it hadn't been for having to modify the cbe battery charge module.
Simple drop in but 2 years in preparation. Ps no mains charger as don't use ehu, so just turn off existing one a low power one supplied with battery.
The Resting or winter charging held by use of a Battery negative Issolator, is again a compromise, but works. so I've added an extra level of control. The control location could be tweaked (ie the charge going to the battery) but the system is proven to work. Simply I use a BMV712s ability to control a SSR based on SOC. Currently for winter i set the limmits to 65% relay off 40% on (ie allow solar charge) . For summer could reset to 90% max. I Have 2 circuits one 1 330w solar panel to SSR to Votronics MPPT. 2nd 220W to Duo MPPT Bat 1 to SSR2 to LB, Bat 2 trickle charge to SB. THe Votronics B2B currently is allowed to just do its thing. The SSR use 15mA 12V auto relays 300mA.
I personnaly don't use EHU sufficient to worry about (I have a small Lithium profile charger if really required.)
As to drop in Mine is a 2017 Ducato Euro6 so a drop in apart from resizing wiring adding a b2b ignoring the EHU then drop in.

Given the right starting conditions and accepting the non ideal conditions you could just drop in ,but , by now you should have realised that LiFePO4 is not another variant of Lead acid and for optimum life and use changes are lickly. As been said before What changes depend on what youve got and how you intend to use it.
The one issue not yet addressed in this thread is "What do you do when not using it", eg winterisation. but this is long enough

 

[gerry mcg]

The problem with the Gel setting is the 16 hour absorption phase that a lot of chargers have is not good for Lithium.

That is why I took the EBL119 charger (that only has AGM or Gel profile) out of the loop and added in a 15A Victron charger with a dedicated lithium charging profile

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