Mixing AGM and Wet Cell Battery Types

[RAW]

I have done a little bit of research and I am coming to the conclusion that if the battery charge parameters in technical details are pretty similar than mixing battery types should not be too much of an issue. I understand that best practice would be to have an array of the same battery types but I am pretty sure I can chuck the AGM I have, this one:
www.alpha-batteries.co.uk/leoch-160ah-agm-leisure-battery/
into a circuit with THREE of these
www.alpha-batteries.co.uk/12v-90ah-bosch-powerframe-leisure-battery-l5013-lfd90/
without causing terrible damage to any batteries.
Now I understand that with the AGM the charge cycles are greater at 600 vs 200 for the Wet Cell, so potentially the Bosch batteries could wear out faster than the Leoch AGM but my feeling is that I can "get away with" pretty much mixing the 4 Batteries to give me MAX 520AH which I think should be sufficient for up to a week off grid using diesel heater, LED lighting and some tech.

Thoughts, anyone ? TIA

 

[wildebus]

well, it won't be optimum, but it will give you power
You will be fitting the Victron BMV monitor to the system I am presuming? What you will need to do when setting that up is to do a usage test.

STAGE 1
charge all the batteries individually to full charge;
connect them all together (have you determined how you will be cabling them all up?)
Reset the BMV so it has zero Ah and is at 100%. You could set the battery capacity at 520AH if you want?
Apply a constant steady load of around 20A (that will give you an approximate discharge rate of C20 - the total capacity of your 4 batteries if all still optimum is actually 415AH, not 520AH))
you should be at half power after around 10.5 hours and 210Ah of draw and the voltage - once the batteries are allowed to rest for a couple of hours - will be around 12.05V. These would be around the numbers you are hoping for. IGNORE THE BMV SOC% VALUE!!

What you need to basically do is stop the discharge when the voltage hits around 12.02V (use the BMV settings to set an alarm when that figure is reached), cut the load, leave for a while and see what the voltage is and what the AH used is. Once the load is removed the voltage probably around 12.05V. If more, add some more load for a short time to get that voltage figure.
Double that Ah figure and THAT is your theoretical battery capacity.

STAGE 2
Charge all the batteries again individually.
connect together again
Set the Battery Capacity on the BMV to the new battery capacity reached from the end of Stage 1
Apply another constant load at the rate of 1/20th of that capacity (so if it was say 350Ah, create a load of 17.5A)
After 10 hours, the BMV should say 50% and the voltage - once load removed and batteries relaxed for a while - should be at 12.05V plus +/- a couple hundreths of a volt.

Completing Stage 2 should confirm the capacity of your battery bank and allow you to use the BMV as a calibrated SOC Monitor.


Finally, you know the history of the Leoch 160Ah battery. But you don't know anything about the 3 powerframe 90Ah batteries, so you could do the above tests in Stage 1 + Stage 2, just using the 3 batteries to give you the AH of THAT bank, then add in the 145AH of the 160AH Leoch to give you the estimated total capacity of all 4 batteries together? (PS. 145AH is the C20 rating for the 160H battery. the BMV wants the C20 value to be entered)

 

[RAW]

THANKS @wildebus - Very helpful
I think what I might do when I get the Van back is measure up for new cables, look at integrating a new Charger (Victron) for 240V. Then get some kit from you to re-wire, do the VSR front-back, and then maybe strip out current wiring and re-wire the 12V System and integrate better ways of switching devices on and off

 

[wildebus]

You have seen the Victron Lynx Distributor Boxes which are an excellent way to connect multiple batteries. However they are expensive there is no doubt, but they have high capacity busbars which is essential if using high current loads (for example, like the AC loads I have).
You have a different type of use and for YOUR setup I would use one of the fuseboxes that SquirrelCook posted a picture off (copying below)

You would have equal sized (gauge and length) cables to each battery - I would go for 16mm2, and each battery will have its own individual fuse protection. Then out of this fuse box you would have a single +ve and a single -ve cable (probably each 25mm2 I would suggest) to go to the 12V camper system (and if you were to go by my conceptual diagram, you would connect this "Battery Bank" combiner/fusebox via an isolation switch to another identical fusebox to use to distribute the +12V to the solar, charger, VSR, 12V blade fusebox, etc.)

PS. using a fusebox like the above makes it very easy to isolate individual batteries if you wanted to charge singlely, or check a single batteries voltage at any time (I have done just that with my Victron Lynx setup - just the same, just bigger).

 

[RAW]

I did a reverse image search on the image above @wildebus and only found it after retrieving the name on Auction sites in South Africa.
The name I came up with was ITZFOSS F371

I can't find one so far on Banggood or EBay or Amazon, any ideas @SquirrellCook ??

On the Talbot I bought one of these which is not the same

That is listed on EBAY as www.ebay.co.uk/itm/112591659554

You say each battery should have it's own fuse protection, what should that be between the batteries, how large a fuse or does that just depend on the total max load that could be applied in the 12V System ? Inverter is Max 3000W at 240V so That would mean a potential draw of 12.5 Amps, so 20AMP Fuses between batteries @wildebus ??

 

[wildebus]

The ones you have above are nice enough. I have a couple of those in my van but the one I showed in my earlier post are a better option for a number of reasons.
I can supply those along with the cables. SquirrelCook posted a link where you can get them from as well.
What I do recommend with these is you use Ferrules on the end of the cables that go into the hole and gets clamped down for best connection.

Fuse Size. your calculations are not taking into account the 240V to 12V conversion - same power with a 20th of the voltage means a 20x bigger fuse requirement remember.
I didn't realise you would be using a 3000W inverter - that puts a bit of a different spin on things TBH. if you were to pull around 2500W, you would need significantly bigger cables then I was talking about. You need cabling from the battery bank to support around 250A, which a 25mm2 cable is not thick enough. That fusebox will not take the cable size that a big inverter would demand.
In terms of individual battery fuses, I would go for something like 80A for the 90Ah Powerframes and 100A for the 160Ah Leoch IF you were using a box that supported the right cables (e.g. the Victron Lynx distribution box).

 

[SquirrellCook]

It was in “Let the fun begin “.

I did buy one and am happy with the product, though as yet not tried. Yes Dave ferrules

 

[RAW]

I didn't realise you would be using a 3000W inverter - that puts a bit of a different spin on things

For clarification, this is the inverter I have

EDECOA Pure Sine Wave 1500W 3000W Power Inverter 12V 240V LCD 2*2.1A USB Ports | eBay

POWER INVERTER 1500W 3000W DC 12V AC 240V PURE SINE WAVE Converter LCD UK OUTLET. "This is a 12V 1500W pure sine wave inverter. Pure Sine Wave inverter : better than modified sine wave, cleaner current in your hands; it prevents crashes in computers, reduces noises in fans, TV and other devices...

www.ebay.co.uk

It is 3000W Max and 1500W straight. I don't know if that makes any difference to your calculations, it sounds like the more copper is in the cable then the more it will cost !! ??

 

[RAW]

It was in “Let the fun begin “.

Not sure what you mean by It was in “Let the fun begin “. @SquirrellCook ??

If it was in a post could you copy and paste the link please ?

 

[wildebus]

For clarification, this is the inverter I have

EDECOA Pure Sine Wave 1500W 3000W Power Inverter 12V 240V LCD 2*2.1A USB Ports | eBay

POWER INVERTER 1500W 3000W DC 12V AC 240V PURE SINE WAVE Converter LCD UK OUTLET. "This is a 12V 1500W pure sine wave inverter. Pure Sine Wave inverter : better than modified sine wave, cleaner current in your hands; it prevents crashes in computers, reduces noises in fans, TV and other devices...

www.ebay.co.uk

It is 3000W Max and 1500W straight. I don't know if that makes any difference to your calculations, it sounds like the more copper is in the cable then the more it will cost !! ??

OK - so it is a 1500W Inverter (the peak value is only relevant for a few seconds if that so you would fuse for 3000W but cable for 1500W (cable that can sustain the current to deliver 1500W can cope with 3000W worth of current short term).

Now to deliver 1500W of power on a 12V battery system will draw say 140A - this is more realistic an option.
Going back to that fusebox, I just did some testing on what battery cables it will suppor on the main busbars in/out, and the individual fused circuits and it is a bit better than I expected and I think it WOULD suit your setup with a 1500W Inverter (not the 3000W one though).

Here is a photo of one of those Fuseboxes with a few cables test fitted ...

For the individual circuits (These are at the top and bottom), 16mm2 and 25mm2 cable work fine. 35mm2 cable is too large to reliably fit without 'birdcaging'.
For the main in/out connections (these are at the left and right), 50mm2 is a good fit. 70mm2 will fit but is tight.

For YOUR setup, I would ideally use 25mm2 cable for each battery but 16mm2 would really be ok but would get warm when the inverter is in use. the Cable in and out I would ideally use the 50mm2 cable, but 35mm2 would also do the job (but like the 16mm2, expect it to get warm when the inverter is at full chat).
The following shows a typical chart showing the ampacity (current carrying capability) of various cables - https://www.powerstream.com/Wire_Size.htm . Take note of columns 4 and 7.
Note that voltage drop is just as important as current carrying, which is why the cables I am suggesting are not the minimum size the charts may suggest. Also the Inverter should be as short a cable run as you can make it.

 

[RAW]

I have just seen this on Facebook and am thinking about getting it as not that far away, not sure the Panel will fit on the Merc but I can use it down the timeline on an off-grid set-up, the Inverter is better than the Edecoa that I have but is 1800W rather than 1500W; so if I used that then I guess 25mm sq cable should be the go ?

Can you give me a ball park on cables plus the SCR Kit with the Victron Cyrix bearing in mind I will likely have two batteries at the front of the Van and two at the back. THANKS as always for your informative assistance

 

[Nabsim]

What do you rate your 24 hour usage as?

 

[wildebus]

cable price is a very volatile thing as it depends so much on the price of copper. The heavy cable can double in price from a supplier overnight.

Two batteries at the front and two at the back? these are the Leoch and the 3 90Ah Powerframes? if so, why do you need to fit them like that? it is not optimum to say the least.

 

[RAW]

What do you rate your 24 hour usage as?

Not sure TBH, running an EE Wifi HotSpot 24/7, possibly 0.5 A/H, Diesel heater a few hours, I have not had the Merc long, then charging a laptop and a couple of phones, an educated guess would be maybe 40 Amps over 24 hour, so I might get 4 days or so from the batteries that I have at a guess

 

[RAW]

Two batteries at the front and two at the back? these are the Leoch and the 3 90Ah Powerframes? if so, why do you need to fit them like that? it is not optimum to say the least.

Not sure I could fit all 4 in the Box at the front, and possibly because now there is two at the front and one at the back, though if I was rewiring then I guess I could put them all closer together if that is best practice ?

 

[wildebus]

The first thing I would do without putting in significant effort into rejigging everything is to check the batteries are good and have a decent charge. The last time I came across someone who bought a set of second-hand batteries (just like you have even though they came with the van) it turned out one battery was shagged and the other two (or three? can't recall if it was a bank of 3 or 4 batteries) were poor. He will be replacing them before the spring I believe

 

[RAW]

The first thing I would do without putting in significant effort into rejigging everything is to check the batteries are good and have a decent charge

I have had them all checked at Halfords and they said all were good, last week that is.

 

[wildebus]

Sorry Robert, but I doubt very much Halfords did a test that told you the capacity of the battery. I would think they maybe checked the suitability of the battery to start an engine?
But anyways, if you are happy with the condition of them then that is the main thing

 

[RAW]

Was with a Yuasa tester like this:

MDX617P - Testers & Battery Analysers - Chargers and Accesssories

<p>Yuasa's range of automotive and motorcycle battery analysers ensure the most up-to-date and accurate test results. A custom made solution that enables potential cost savings and increased revenues. Test more batteries and sell more batteries.</p> <p

www.yuasa.co.uk

 

[Nabsim]

Not sure TBH, running an EE Wifi HotSpot 24/7, possibly 0.5 A/H, Diesel heater a few hours, I have not had the Merc long, then charging a laptop and a couple of phones, an educated guess would be maybe 40 Amps over 24 hour, so I might get 4 days or so from the batteries that I have at a guess

Going of that I would guesstimate around 20 amps. Was just the I had 3 x 90ah PowerFrames and my useage pattern killed them in a little over 12 months. I draw 65 amps a day, am always in the van and very rarely use hook up though.