DIY Lithium

wildebus

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Is that just at tick over ? Does it get better at say 1k5 rpm?
I don’t think it unreasonable to expect a modern alternator and regulator to hold nearer the 14.2v with a 40a load.
The numbers were idle but I don't think it makes that much difference.
Same timeline and added the current (this is the current into the Leisure Battery, so the B2B is pulling more (charger inefficiences plus around 1A the system is using) and there is the 12V into the Fridge as well. But the Current is fairly constant and the voltage varies by maybe around 0.1V and each of the 3 seperate driving sessions are pretty well the same (with Lights on - so an extra 10A load or so - on the 2nd and 3rd sessions).
1608383359074.png


I don't think Alternators fitted to vans as standard are as high & precision bits of kit people think they are!
 

Markd

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No, still a way to go.
Just gone out and checked the Starter Battery voltages at different points ...
Running, no "extra loads" (so engine idling, no fridge, no B2B connected) - 14.28V
Running, Fridge on 12V, no B2B - 14.16V
Running, No Fridge, B2B Connected and outputting 33A - 13.44V
Running, Fridge on 12V and B2B outputting 33A - 13.29V

B2B outputing 33A - say 80-85% efficient, so pulling about 40A out the Vehicle system?
Seems quite a drop of voltage when the Load is increased? :unsure:
If you are delivering 33A to LB that will be at more than 14v presumably (14.3v maybe?) so the input current to B2B @ 13.3v will be a good bit higher - as you say could be 40A with some conversion losses.
The alternator copes quite well with the fridge which could well only be 120w for a standard fridge (my fridge freezer is 175w apparently)
When I was doing fuel consumption measurements for various electrical loads on my Passato at tickover speeds I had 13.4v in the system so your voltages are respectable enough I'd say.
A few more revs help improve current output but won't do much for the voltage.

I agree with your comment about alternators being fairly basic beasts - they are great at keeping starter batteries topped up as those never really get low.
On the other hand start taking regular sustained heavy currents - think running inverters at tickover or replenishing big LB banks will heat them up and find any inherent weakness.
 
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Technispark

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My cousin builds these for electric bike conversions for himself and his retired friends, but although I am a retired electrical engineer I don't think I am going to risk it for my T5 camper. I shudder to think about the potential for damage should the battery 'auto ignite'
 

Philip Tomlinson

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My cousin builds these for electric bike conversions for himself and his retired friends, but although I am a retired electrical engineer I don't think I am going to risk it for my T5 camper. I shudder to think about the potential for damage should the battery 'auto ignite'
I am guessing he is using different lithium chemistry, LiFePO4 batteries are very safe.

 

Philip Tomlinson

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For those interested I have put a link to the type of IC used in most modern Bosch alternators.


An alternator that has a regulated output of 14.25v will not read at 14.25v in any circuit that has a resistance unless there is no load. A vehicle has cables and a starter battery (a load as even when fully charged they still draw current) in the circuit.
 

Markd

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My cousin builds these for electric bike conversions for himself and his retired friends, but although I am a retired electrical engineer I don't think I am going to risk it for my T5 camper. I shudder to think about the potential for damage should the battery 'auto ignite'
Very sensible decision - if you don't feel competent about doing something then don't do it.
 

Markd

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DIY batteries? Of course very few people would have tried to construct a DIY lead acid battery. Bit on the iffy side that.
Going back to original post.
I have seen YouTube videos of people stripping down old batteries melting down the lead, recasting and rebuilding - then just pour back the old acid and away you go.
Simples really 😀😀😀
 

Harryw

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Following on from the alternator side of this thread. I checked my van battery today and that was down to 12v as it’s been laid up for a month. The Leisure batteries were full charged ish at 12.8v.
On start up I measured across the van battery and it pretty much instantly went to 14.2v and I presume onto a heavy charge load, but with 14.2v remaining across it, which is what I’d expect from the alternator voltage regulator to be doing, with minimal voltage drop between the alternator and van batt cabling/connectors. I monitored the leisure batteries at the same time via the smart shunt. That went to 13.7v and started at a 20a draw. As that draw went down it, as you’d expect with less current, it stabilised around 14.1v. I think my cabling and or connections between the van battery to leisure batteries must have around 0.025ohm between them, not ideal but not world ending either.

However one thing I noted was when I first turned the ignition key to power on before turning to crank over I noted a 6-8a draw from the leisure batteries.... do I have a VSR/blocking diode problem? Everything else functions as you’d expect...
 
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Harryw

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Not auto step retraction when you turn ignition key?
That’s a good idea, the step was already retracted at the time, but I suppose it could still be being cycled through though.
I only accidentally observed it when about to monitor alternator input on start up. I will investigate further another day, thanks.
 

Markd

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FWIW my step is powered by van battery.
It has to be otherwise I wouldn't be able to climb in from outside and turn on leisure battery to operate it.
Same getting out during a journey - I don't have to power up habitation before getting out and leave electrics on.
 

colinm

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Going back to original post.
I have seen YouTube videos of people stripping down old batteries melting down the lead, recasting and rebuilding - then just pour back the old acid and away you go.
Simples really 😀😀😀
I seem to recall a film from Cuba where they cut off the top, put in some cocktail of chemicals to clean the plates then refill it.
 

Harryw

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Had another look see today. Definitely not the step, that as already said comes from the van battery.
I’m 99% certain there’s a stuck/welded relay in the PDU control board linking the leisure battery to the van battery when ignition is on and prior to the D+ signal for running engine. Well I assume it has a D+....
The relay/control board is BCA based, although it has an Erwin Hymer Group sticker on it too. See picture below;
94BB9DFF-8545-4DA6-83A1-1C276C48D11A.jpeg

anyone have access to circuit diagrams?


I’m not sure whether to start another thread or not, rather than to continue to take this thread off track.
 

Harryw

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I went for the Lishen batteries and their brand Basen BMS (which is a rebadge Daly BMS)
It’s all your fault 😂

I just purchased a single set and BMS of the same. All in $558 DDP terms by the time you add currency exchange rates and bank fees for the privilege it came to £428, not bad for a 272aH battery.

It’s coming overland and UPS to my door, quoted 40-50 days. I suspect the first leg must be by camel across Mongolia 😂

Did you see Wills latest video? He did a 1C discharge test on the Lishen 272 in a 4S config and got 281aH, here’s hoping...
 

SquirrellCook

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It’s all your fault 😂

I just purchased a single set and BMS of the same. All in $558 DDP terms by the time you add currency exchange rates and bank fees for the privilege it came to £428, not bad for a 272aH battery.

It’s coming overland and UPS to my door, quoted 40-50 days. I suspect the first leg must be by camel across Mongolia 😂

Did you see Wills latest video? He did a 1C discharge test on the Lishen 272 in a 4S config and got 281aH, here’s hoping...
Please post info on your experience, be it good or bad. I'm yet to buy batteries for my build yet and your numbers are looking tempting.
 

Philip Tomlinson

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It’s all your fault 😂

I just purchased a single set and BMS of the same. All in $558 DDP terms by the time you add currency exchange rates and bank fees for the privilege it came to £428, not bad for a 272aH battery.

It’s coming overland and UPS to my door, quoted 40-50 days. I suspect the first leg must be by camel across Mongolia 😂

Did you see Wills latest video? He did a 1C discharge test on the Lishen 272 in a 4S config and got 281aH, here’s hoping...

On Will's forum, many members have had the Lishen 272 and have report 280-285Ah capacity. Aimee did send me the data and test results for the Lishen cells and they do look good.

I will test all my gear and post a video once it all arrives.

Phil
 

Harryw

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Yah, mine have just been shipped and these ones are Eve LF280 B manufactured 23/12/20 not Lishen as expected, not a problem per se. I too have the data sheet for them, states minimum 280aH typical 285aH. Do you want a copy of the file for the archives, it’s a pdf?
 

SquirrellCook

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I am installing a 1120Ah LiFePO4 bank in my motorhome soon. This is made of 16 x 280Ah 3.2V EVE prismatic cells and 4 x Daly 100A Bluetooth BMS. The cells fit into the battery trays that I already have, in fact, they are 3cm shorter. Later next year I am going to add heater pads to the cells and a charge flow control system.

I would like to give you the exact price but at the moment it is uncertain because of upcoming changes to customs and trade agreements so I can't order them until the 2nd January and the USD exchange rate may have changed by then. The parts cost including the busbars, BMS, Bluetooth module, cells, shipping, customs clearance and VAT comes to $2158 USD (£1622.93) which is less than £1.50 per usable Ah.

You could of course just order 4 cells and one BMS which would cost £410 for a 280Ah battery.

Compare these two:

280Ah DIY LiFePO4
cost £410 (280Ah 100% useable) £1.46 per useable Ah. 3000 cycle life X 280Ah = 840,000 Ah delivered @ £0.49 per thousand Ah delivered

Varta LFD90
cost £90 (90Ah 50% useable) £2 per useable Ah. 200 cycle life X 45Ah = 9,000 Ah delivered @ £10 per thousand Ah delivered


THE CONS ARE

That you have to deal directly with the manufacturer in China through a website like Alibaba.
Although the parts may come with a warranty I would not fancy trying to make a claim.
You need to make sure the cells are charged to the same level before connecting them together.
You will need to build some kind on an enclosure for the battery.
The battery will not have a low-temperature cutout.
With prismatic cells, the max discharge current is normally the same as the capacity, so a 280Ah battery may have a max continuous discharge current of 280A.
If you want to run a big inverter (mine pulls 400A) you will need to make sure that the BMS is big enough to do so.
You will still need to survey and maybe upgrade you charging systems for the requirements of LiFePO4.
You do need to have some electrical competence to do this.

Phil
Did you make any progress with this Phil?
 

Footloose

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Hi Folks
First ever post in ANY forum!
Built this Li-ion battery to power my electrified Brompton and "electric scooter" (I know at 72 I should know better). 30 Samsung 30Q 3000 mah 18650 cells @ around £2-65 each from Fogstar in UK. Configured 3 parallel and 10 series = 9A x 37v but obviously can be arranged in any which way eg. 7p x 4s = 21A x 14.4 V. The Razor scooter is a wolf in sheep's wooly stuff, with the Li-ion and bigger motor it zips along at errrmm !! Now fitted with disc break ! So is this info of any use to you guys considering a battery build for your vans?
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