Bad Cell?

[boB]

What I do is to at least try charging the individual battery with its own charger.  In this case, you'd probably
have to just treat it as a 6 volt battery unless you have access to the individual 2 volt cells, then it could
possibly work much better for that one bad 2V cell.

Vtmaps suggested that while charging the batteries, check the voltage across the 6V batteries and see if
that one bad one is at a low or a higher voltage than the good batteries.  This is what I was going
to say.  Also, under charge, is the bad battery warmer than the others.  If the bad battery is
hot and lower than 2V, then it may be shorted and make that string draw down your good string.

BUT, I wouldn't think that would drop your entire string down to 2V below normal charge so shouldn't
harm the entire bank at least.

What is your nominal bank voltage ?  If it is 48V, you ~could~ remove the bad 6V battery from the
one string and remove a good battery from the good string and just operate at 6 volts less than
nominal for a while and adjust your charge voltage accordingly.

boB

PS  Good !  I see...
"Battery Bank Surrette 800aH @ 48VDC 38,400 watt hrs."

The Magnum should work at the lower voltage.  ( I think. )

[plongson]

String 2 is holding steady so far. It's only a few points in SG below S1 but still needs some EQ I'm thinking. At least with Thanksgiving here, we'll be running the genset more and I'll get some good charge time.

This stuff always happens when you need it most...like Thanksgiving.

The bad battery I replaced was naturally in the back and the hardest to get to. I installed a Unistrut trolley to pick it out with a come-along and I'll use it to hang a outdoor shower bag for watering duties (seen ready to hang in the background).

[dgd]

A month ago I had a "bright idea" for an extensible way to accurately monitor an arbitary number of cells. I've designed the beast, layed the board and sent it off to be fabricated. Expecting it back soon. The basic idea is each board is a stand-alone subsystem that will monitor three cells. Differential amplifiers allow the on-board processor to do Analog conversion for each cell to about 5mV. Each board will talk to the next (and listen to the previous) so they all know what the entire string is doing. They will be able to give you a warning when one cell is outside your chosen limits from the others. It has a serial interface to send cell  voltages to a monitoring/logging system. I also added temperature sensors for each cell.

Designed for lead-acid (2V cells), it'll take 2 boards to monitor a 12V system, 4 for a 24V and 8 for a 48V system. I've designed it so it should work for cells as low as 1.2V/cell, and as high as 3.6V/cell. Should work for NiMh, NiCd, lead/acid, lithium etc.

Ross,
This looks interesting - early detection of a suspicious or failing cell. I assume its main function is to protect the remaining good cells and especially in parallel string configurations where we don't want a failing cell in one string flattening the other string (as may be the case with plongson's system).
Please add me to the customer list
dgd

[RossW]

This looks interesting - early detection of a suspicious or failing cell. I assume its main function is to protect the remaining good cells and especially in parallel string configurations where we don't want a failing cell in one string flattening the other string (as may be the case with plongson's system).

Well, a long list of friends who've suffered a loss of a cell, or "found" a cell way out of whack. (myself included).
Majorly expensive 24-bit ADC and many-channel multiplexors and all the grunt to process it wasn't appealing.

The boards turned up a couple of days ago (caught me off guard), so I ordered the rest of the bits I needed on thursday.
Friday the resnets and processors turned up (only).

I've assembled what I can of two boards: one (the small one) is just a 3-cell board. The larger one is the same 3-cell board PLUS the isolated RS232 interface for the logging machine (if used). Two pics, one of either side. Hopefully the rest of the bits will turn up in the next few days and I can start writing some code...





The longer connector is 0/2/4/6V (3 cells), and the optional 3 temperature sensors. (one per cell)
The two 2-pin connectors on the short end are for the daisychain in and out connections to next/previous board.

[boB]

RossW, looks like you might also be waiting for a 9 pin D-sub connector.

Hope when you get all your "bits" that they are in the right order.

What make of resistor networks did you use ?  I wish there were res networks
that were cost effective against lots of individual resistors.

boB

[RossW]

RossW, looks like you might also be waiting for a 9 pin D-sub connector.

Yes. And that thing is bigger than the rest of the board together!

Hope when you get all your "bits" that they are in the right order.

Me too   I only used the 1N914 diodes because I have a few thousand left from my old prototyping days.

What make of resistor networks did you use ?  I wish there were res networks
that were cost effective against lots of individual resistors.

I have built this to use 0.5% Vishay resnets for the opamp feedback and dividers, but at $1.40 each or something stupid it was hard to justify. So I used ordinary Bournes resnets, even in my low quantity prototyping application they came out at about 2.6 cents each - and are quite frugal with how little board space they need!

I layed the board so each opamp uses 4 resistors in the one resnet - hoping that they would all drift equally together with time and temperature. I measured several of them, and while nominally 10K, they were all within 100R of each other (so basically, about 1%) - I figure I can always swap them out if need be, but at this stage, 1% is perfectly fine! (and certainly for prototyping!)

In the back of my mind is being able to store calibration constants in FLASH (I have 256 bytes of NV storage), so each of the 3 A-D channels could be calibrated after manufacture, if required. (I already did this on my tracker controller. Saved a bunch of trimpots to set gain and offset!)

[plongson]

Surrette isn't impressing me in the support and warranty department. I sent off all the required paperwork to Steve last week and still no feedback. I purchased and installed a new battery on my own just because I thought this might happen. Can you imagine sitting around in an off grid system in the winter waiting for a warranty battery?

What a bunch of hooey. Lack of service like this, mostly the lack of any feed back will not make me a return customer.

Someone hast's be proud of me, I didn't even use any expletives this time to describe Surrette...LOL

[Westbranch]

Good Boy... now sit and behave 

[dgd]

What a bunch of hooey. Lack of service like this, mostly the lack of any feed back will not make me a return customer.

Everyone I know that has had a failed battery always never bought the same batteries again.
For most people it just too  risky as confidence  in them is reduced
dgd

[Halfcrazy]

Surrette isn't impressing me in the support and warranty department. I sent off all the required paperwork to Steve last week and still no feedback. I purchased and installed a new battery on my own just because I thought this might happen. Can you imagine sitting around in an off grid system in the winter waiting for a warranty battery?

What a bunch of hooey. Lack of service like this, mostly the lack of any feed back will not make me a return customer.

Someone hast's be proud of me, I didn't even use any expletives this time to describe Surrette...LOL

Well all I can say is I have learned from your lesson and will "NEVER" use a Surrette battery again in my life time. I need a manufacturer that is behind me when the lights go out. My local battery distributor stocks the Trojan brand and will "Give" ma a new one same day no questions asked (Well as long as it should be warrantied) then argues with Trojan for me. Not that I think Trojan is the best battery but I sure do think my distributor is one of the best and that's important.

I say stand on the mountain top and holler how bad Surrette sucks! I think at this point they owe you a refund as you have already bought the replacement!

Ryan

[tecnodave]

I have been using Interstate for years due to their excellent dealer network support. They have always supported their product even when far away from home. Interstate started as a local California firm but has been bought by Johnson controls and now are nationwide. Their L-16 are manufactured by U.S. Battery Co (another unit of Johnson controls) but have the Interstate label and dealer support network. They have stock on the shelf and deliver the next day. Interstate warehouse in Salinas, CA has 6 L-16's on shelf at all times for user support. The same for Trojan , great support, and I believe that they are still an independent company totally focused on the premium battery market. RE and traction battery is there base.

[Vic]

Hey Paul,

Very sorry to hear of the bad cell,  and the disappointing response from Surrette.

If you bought the original Surrettes from a dealer,  then would hope that the dealer would handle the warranty details for you.

Have been very happy with the Surrette batteries here,  and when noticed early on that one cell had been damaged in shipping,  Surrette sent a replacement cell (dry)  to me immediately.   They even offered to split the freight costs 50-50 with me (usually,  warranty batteries are FOB, NS,  where the customer pays freight).

Do not know what to say,  but seems that you have been very conscientious about care and maintenance of your batteries.

Good Luck,   Vic

[plongson]

I emailed Steve at Surrette this morning and got a pretty quick reply that all my forms and email went into his trash bin. I needed to resend everything for him to evaluate. At least I got a reply, that's a good sign. If they honor the bad battery will even be better...

Ya, it's just my luck, I baby those batteries and even tuck them in at night with a little teddy bear, and what do they do...go caus'n trouble...HaHa.

What's got me lay'n awake at night now is the charge imbalance between strings. There is actually a couple of amps difference from the interconnect on string 1 and string 2. Add them together and you get the amperage on the big feed line to the inverter.

All the interconnects and crossovers were meticulously removed, cleaned and gooped up with that wazoo anti-corrosion stuff in a can. There is no connection problem there, it just has to be the resistance in the batteries (I'm out on a limb here and guessing).

When I left on Saturday everything looked great, it snowed yesterday and the panels were slabbed with snow all day today (watching from IP cams on my phone). Hope the snow slides off and the sun gets it going tomorrow. Got the Kubota dialed in just in case...it was in the teens' all day.

[Westbranch]

Hi Paul Good News!?!

Well anyway, I thought I would share a pic of our recent, all time 24 hr record snowfall here in Williams Lake.
click on the paper clip to get a good view.. don't know how to insert a bigger pic like you did...?

[plongson]

HOLY CRAP! Now that's some snow! It looks like it would be tough to even get out and going in that stuff.

I'm in Las Vegas right now where it's a bitterly cold 40*f. I have to go to Ft.Dodge Iowa next week and that's not going to be any fun but cold is one thing, that white stuff is just plain miserable.

I've posted this link before, but if you have nothing better to do and want to waste some time, click on http://barkingdoglodge.com

There are some IP cams and a link to the Magnum MagWeb inverter page. It's a lot more interesting during the day. This is one way I keep an eye on things when I'm on the road.