Hi Harry.
I REALLY hope I am not teaching granny to suck eggs - if so, I apologise, not wanting to rattle cages. Having spent a fair bit of time playing with lead acid over the years though, the voltages had me reaching for a calculator. If I have made an assumption that I shouldn't (not standard Pb/H2s04 etc), then just ignore me and I'll go away quietly
Anyway....
175 volts over 14 cells is 12.5v - if that is an off-load voltage once the battery has rested a few hours from being charged, it suggests that the battery is between about 75% and 80% charged at most.
If it is a voltage measurement taken quite recently after a charge, then the battery capacity is currently MUCH lower than this. If the voltage has since fallen further, you could then find out roughly what the final pack voltage was - and get a fairly good idea of amount of oomph left.
100% = 12.83v
90% = 12.70v
80% = 12.55v
70% = 12.45v
60% = 12.30v
50% = 12.18v
40% = 12.07v
30% = 11.93v
20% = 11.82v
10% = 11.65v
About 10.5V under load (20-40A on a normal sized car battery) will indicate a battery almost totally exhausted - I appreciate fully that you are applying more than that when trying to pull off BUT nonethless it is pulling the battery voltage down to below the "empty" range. Unless you are pulling many hundreds of amps, you should not be finding this on even an old tired car battery if it reasonably full.
When a lead acid has just been taken off from being freshly charged, it will often show over 13.8v which will quickly fall to around 13.2v and then GRADUALLY fall away to a gnat's whisker above 12.8 for a completely full battery. Although 12.5v is far from flat (assuming this is a "rested" voltage once the surface charge on the plates has dissipated), it is certainly only about 80% charged at best - if it was at this voltage soon after coming off charge, then it was VERY MUCH lower.
Initial thoughts:-
Check to see if all batteries are same voltage - and nothing quirky going on with a failed battery in the middle (even a tiny bit under voltage might suggest a high resistance cell which will (literally and metaphorically) buckle under extreme load.
How good are your wire links - are they all in good condition and making superb contact?
To give 14 normal lead-acid batteries in series a decent charge, they need to be fed around 196v as a minimum - and ideally an
occasional equalisation overcharge to around 210v (15v per battery for half an hour or so).
At the end of the charging cycle, battery off-load ought to show 189v-193v or so (13.5v - 13.8v per battery) which will fall to around 185v (13.2) in the space of a few minutes and then a few hours later ought to have settled down to around 179.2-180v (approx 12.8v - 12.82v per battery).
At this point (once fully charged), I am hoping you will find a much more heartening result, if not, then assuming all batteries are good, I am wondering if there is some iffy connection somewhere which is warming up nicely.
Incidentally, are these new batteries or ex-use ones you are using?
As I said earlier, if I have missed something or come over as some smart-ar** know all, it REALLY isn't my intention but having played around with chargers, batteries, UPS gear and PWM controllers, and generally learning the hard way, I ended up knowing a fair bit about the regular lead-acid battery and how the off-load voltage can be VERY deceiving at times. If I can be of any help at all, please shout me on here or privately.
Kind Regards
Mark
