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Offline sdunn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #60 on: June 26, 2016, 06:28:10 pm »
First rundown test:
Voltage at start: 13.23
Amp-Hours used: 28.4
Elapsed time: 8.5 hours
Voltage at end: 13.12

For now, 12.00 volts is going to be my "don't go below" number. Looking promising.

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Offline BobB

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Re: Winnebago AUX/house battery, solar thread.
« Reply #61 on: June 26, 2016, 07:26:26 pm »
Did you do the "bottom balancing"?  how did that go?
BobB
'99 VW EVC

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Offline albertr

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Re: Winnebago AUX/house battery, solar thread.
« Reply #62 on: June 27, 2016, 10:49:52 am »
Albert,

Not sure, but I think the Zamp works connected to a single 12V battery bank (even if made up of several 12v batteries in parallel) - a BMS (or EMS as sometimes referred to) is necessary to balance the individual cells.  The Zamp does not balance the LiFEPO4 cells, it just provides a chargin profile suitable for LiFEPO4 batteries.   On some other forums, people have been connecting it to banks made up of 12V LiFePO4 units, each with integral BMS.  Other than Technomadia, who made their 12v units up from individual 3.2 v cells,  most have been buying 12V units from places like Stark.

I took a look at Stark Power and Smart Battery, and I'm not sure if they have a real system to balance cells either... Based on the pictures available on their websites it looks more like overvoltage/undervoltage/termal protection? Looks like they are building their batteries using many small cells, so if their battery comprises a few dozen of small cells (some connected in series, other connected in parallel), how much would the cost of complicated system to individually balance and maintain them?

I'm curious if these Chinese cells from EVTV are also build from many small cells connected in parallel?

On a side note, cheap Chinese LifePO4 18500 can be found for a couple of bucks a piece, if anyone can design and manufacture a controller which can monitor/balance/maintain/charge a few dozen of 18500 cells, it might be an interesting DYI project to build a LifePO4 battery out of them. Additional benefit would be very low cost of maintenance and repair. If controller has ability to automatically identify a bad/degraded cell, just swap it out with a brand new spare 18500! Can easily  be done in the field.

-albertr


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Offline sdunn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #63 on: June 27, 2016, 11:06:19 am »
BobB: Have not yet done the bottom balance. You can do it at any time so long as you have not damaged any of the cells. My pack is so small and easy to break down that I got impatient and wanted to see it perform. In an EV application, with perhaps dozens of these cells, once you assemble you are highly unlikely to break it back down, so probably important to do it upfront there.  If I get capacity that I am happy with (and I can watch voltage very carefully) I may never do the balancing.

AlbertR: The CALB cells are single cells. 180 ah is currently the biggest available, although if you are set up to do business on Alibaba, I think I saw some 200 ah cells there. In a year I wouldn't be surprised to see 250AH widely available.   

As near as I can tell, bigger is better with respect to AH/cell volume  and $/AH.  When I bought my 180s, EVTV had some 100AH cells on a closeout deal, but the 180s turned out to be very similar in $/AH, and I get the simplicity of a 4-cell pack.

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Offline BobB

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Re: Winnebago AUX/house battery, solar thread.
« Reply #64 on: June 27, 2016, 11:28:23 am »
I took a look at Stark Power and Smart Battery, and I'm not sure if they have a real system to balance cells either... Based on the pictures available on their websites it looks more like overvoltage/undervoltage/termal protection? Looks like they are building their batteries using many small cells, so if their battery comprises a few dozen of small cells (some connected in series, other connected in parallel), how much would the cost of complicated system to individually balance and maintain them?
-albertr


Albert -  on the Stark site they say:

"StarkPower “DEEP CYCLE” Models have a Battery Management System (BMS.) BMS monitors the key operational parameters during charging and discharging such as voltages, currents and internal temperatures.

There are three main objectives common to all Battery Management Systems (BMS):

Protect the cells in the battery from damage through overcharging or discharging too low.
Prolong the life of the battery with cell balancing.
Maintain the battery in a safe operating state."

This "BMS" or "no BMS" is an interesting discussion.  On other RV forums I follow, it is always "must have BMS".  Have never seen/read/heard the "no BMS" topic before.  This discussion seems particular to forums/blogs on electric vehicles.  Just wonder if the type of use/power demand for electric vehicles has anything to do with it.  RV use is for lights, fans, fridge, run an inverter for some 120V appliance, etc.
BobB
'99 VW EVC

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Offline sdunn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #65 on: June 27, 2016, 11:53:03 am »
In my humble opinion, which is worth exactly what I charge for it  ;) ....companies like Stark are making "drop-in replacement" batteries, which are designed to have *some* tolerance for operator neglect or just plain indifference.  It may very well be the case that if you are going to sell a "drop it in and forget about it" product, the BMS is a very good idea.

Also, if I have a class A coach with a 500AH or higher pack, then that is a very large investment, and I may think that a BMS protects that investment. I've yet to see data that proves anything one way or the other.

At present, the premium for that kind of product is high (vs. DIY-ing it) and I'm willing to pay close attention to my pack in order to get the potential benefits at lower cost. I'd bet that anyone who is wants to build their own EV (convert an existing gas-fired car) is similarly willing to pay a lot of attention to what's happening "under the hood".


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Offline sdunn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #66 on: July 02, 2016, 10:46:27 am »
Update on run down test:
To go from 13.23 starting voltage to 12.8 ("nameplate" voltage on the pack) I used up 71 amp hours. With the Vitrifrigo running non-stop at 3.5 amps, that would 20 hours of wall clock time. However the vitrifrigo is going to be much closer to 1.5 amps over a a 1 hour period, so I think that will give me roughly 40 hours of runtime with no solar re-charge. 

Next step is to see how many amp hours are used up going from 12.8 to 12.0, which is going to be my cutoff.  The vitrifrigo won't cut out until voltage gets to about 11.0, so I have to monitor and hit the battery switch to protect the pack.   

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Offline sdunn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #67 on: July 05, 2016, 05:50:26 pm »
Update on the Zamp charge controllers & Lithium profiles for AlbertR.  They are 'targeting' 'beginning of 2017' for having the Lithium profile on all of their controllers. 

So, if I want one *now* it means mounting the non-weatherized lithium charge controller on the same plastic panel as my monitor & battery switch. I thought this could be an outcome, so I already have the splice between the Zamp plug on the outside and the battery busses. I just need to unplug and plug into the charge controller and I'm all set.

BTW, I stopped my rundown test at 12.5v and 91 amp-hours used.  Hard to say exactly, but given what i saw, starting from a "full charge" of 13.6V, I should at least be within spitting distance of my predicted 144 amp-hour capacity. I'm going to call this whole thing a preliminary success.  ;D ;D ;D


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Offline albertr

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Re: Winnebago AUX/house battery, solar thread.
« Reply #68 on: July 06, 2016, 06:15:59 am »
I'm wondering if were considering adding some programmable BMS like the one below?

http://www.ebay.com/itm/Lifepo4-Li-ion-Lipo-1S-4S-BMS-Programmable-With-LCD-Monitoring-/151644551555

-albertr

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Offline sdunn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #69 on: November 03, 2016, 11:14:41 pm »
First field test for the LifePO4 battery.  I sort of chickened out and added the solar before my first trip (200watts of Renogy suitcase solar; Genasun Lithium charge controller)

Long story short: Conditions were optimal (lots of sunshine, warm nights with no need to run the furnace), but with a load of the Vitrifrigo C60iac, interior lights, constant charging of laptop and 3 iDevices, I made more power than I consumed - the battery never dropped below 13.2 volts, even first thing in the morning.

Next test will be shorter days, and I'm going to add a 2000w inverter so that wife can run a blow dryer. I still expect to have essentially indefinite power.

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Offline mcbbcn

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Re: Winnebago AUX/house battery, solar thread.
« Reply #70 on: August 23, 2018, 03:18:20 pm »
Hi Everyone,

I'm a newbie at this topic and I own a 1999 EVC.  I will be asking some basic questions and if you have the time, please let me know and if you don't that is ok.

The first question I have is: If the EVC comes with a battery isolator, why are people purchasing the Stinger battery isolator? Is that to replace it? Or is the existing one not good enough? Or it won't handle the load?

Thank you,

Miquel

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Offline JimStewart

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Re: Winnebago AUX/house battery, solar thread.
« Reply #71 on: January 21, 2019, 09:32:05 am »
What a good thread!  Thanks to Albert for the write ups that I hadn't seen before.  He ran into similar issues that I did (but planned his install a lot better than me!)

I ended up fitting 4 x 50W lexun flexible solar panels as they more or less exactly fit the width of the central roof section.  Only gets me 200w of course in a series/parallel arrangement.

I started off with a larger panel but it wasn't large enough so it came off and the 200w array went on.

I also went from a Ctek D250SA solar charger + split charge controller to a victron energy Smart Solar MPPT 75/15 as this gives me load and solar monitoring over bluetooth.  It has given me a much better picture of my loads and what I can get out of the 200w panels and has charge curves and battery protection customisable to lead acid/agm and lithium.

I also went from a 110AH lead acid to a 130AH lithium.  The lead acid wasn't storing anywhere like the energy it should have.  My monitoring has only run a few months so far but on a trip my daily usage can hit nearly 400Wh which is basically Vitrifrigo C60i fridge and the stock Suburban furnace + some LED lighting.  That was about all the lead acid held in winter.. .

Next to go on is a Victron Battery monitor, this will give me better battery monitoring but will also disconnect the alternator charging when I hit a preset level to prevent overcharging.

At some point I intend to start writing up some of my own installations. . . . .

As a European, I actually ended up ripping out all the 110v stuff and have not had any reason to put mains back for what I do.


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