Lead Crystal

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23rd February 2018, 04:09 PM
drivesafe

Quote:

Originally Posted by Kidbeen

If you are talking amperage at a 100 ah you would only get the same run time as any other AGM.

Hi Kidbeen and you don't quite understand the difference in technologies.

If you have a standard 100Ah AGM, then you have a total of 80Ah of usable capacity, based on a C20 rating, because most AGMs can not be discharged below 20% SoC without damaging them.

If you have a 90Ah Lead Crystal battery ( 6-CNFJ-90 ) then based on the same C20 rating and the fact your can safely discharge Lead Crystal batteries down to 0% SoC, you have 100Ah available for use. A 70Ah Lead Crystal battery will give you 78Ah of usable capacity. Near equal to that of a 100Ah AGM.

Quote:

Originally Posted by Kidbeen

The lead crystal cost me more than a normal AGM.

But a Lead Crystal battery can be smaller for the same amount of energy required ( see above ) and a Lead Crystal battery will out last an AGM by 2 to 3 times.

It all depends on usage, and the more you intend to use a battery, the greater the cost advantage is to use a Lead Crystal Battery over a standard AGM.
23rd February 2018, 05:15 PM
Kidbeen

Quote:

Originally Posted by drivesafe

Hi Kidbeen and you don't quite understand the difference in technologies.

If you have a standard 100Ah AGM, then you have a total of 80Ah of usable capacity, based on a C20 rating, because most AGMs can not be discharged below 20% SoC without damaging them.

If you have a 90Ah Lead Crystal battery ( 6-CNFJ-90 ) then based on the same C20 rating and the fact your can safely discharge Lead Crystal batteries down to 0% SoC, you have 100Ah available for use. A 70Ah Lead Crystal battery will give you 78Ah of usable capacity. Near equal to that of a 100Ah AGM.

But a Lead Crystal battery can be smaller for the same amount of energy required ( see above ) and a Lead Crystal battery will out last an AGM by 2 to 3 times.

It all depends on usage, and the more you intend to use a battery, the greater the cost advantage is to use a Lead Crystal Battery over a standard AGM.

Thanks for setting me straight. Electronics are not one of my strengths but I thought I would be polite and reply to his question.

I also heard that lead crystal batteries can now be used full time as starter batteries. Is that factual?
23rd February 2018, 05:26 PM
drivesafe

Quote:

Originally Posted by Kidbeen

I also heard that lead crystal batteries can now be used full time as starter batteries. Is that factual?

Hi again Kidbeen, to my knowledge, they are NOT suitable for use as cranking batteries.

I also do NOT recommend their use in engine bays.

A cranking battery version is on the way, but I do not know when they will be available.
23rd February 2018, 08:44 PM
Kidbeen

Quote:

Originally Posted by drivesafe

Hi again Kidbeen, to my knowledge, they are NOT suitable for use as cranking batteries.

I also do NOT recommend their use in engine bays.

A cranking battery version is on the way, but I do not know when they will be available.

Seeing you are the dual battery expert, you will know the answer to this question:-

My starter battery and Lead Crystal battery are connected via a Redarc Smart starter. I have had the batteries fully charged and the red Led was glowing on the Redarc. When I measured both their voltage they were both the same at 12.51V. I have just pulled the following from another forum but it was a 2009 post:-

"Until about 2 yrs ago, the Redarc battery isolators would remain active until the battery voltage dropped to 12.5 volts. More recent models 'turn off' when the battery voltage drops to 12.7 volts. I recently had one custom made & stipulated this cut off be set at 12.9 volts.

The red light will remain on until the battery voltage drops to the cut off level. I found that 12.5 volts was too low if camped in the one spot for around a week. With a start point of 12.5 volts, the battery voltage would drop to about 12v after a week due to the computer type items that keep operating when the vehicle is turned off. Also constant door opening drops the voltage with the internal light going on & off.

The customised Redarc isolator cost $160 in lieu of the normal $100 approx."

What is the science in reducing the voltage to 12.5v rather than 12.7V?
23rd February 2018, 10:14 PM
drivesafe

Hi Kidbeen, the lowering of the Cut-Out/Turn-Off voltage is more to do with the Cut-In/Turn-On voltage level.

Before the introduction of variable voltage alternators, or so called "smart alternators", the Cut-In/Turn-On voltage of most isolators was 13.7v or a little higher for some.

These usually had a Cut-Out/Turn-Off voltage of around 12.7 to 12.9v

This was all good and well until alternators would some times drop below 12.7, turning the isolator off, but then not get back up to 13.7v, so the isolator would remain off.

So they dropped the Cut-In/Turn-On to around 13.2v and at first, left the Cut-Out/Turn-Off as was.

In many cases, because the Cut-In and Cut-Out voltages were now to close, this resulted in the isolator oscillating, continually turning on and off all the time you were driving.

This type of isolator oscillation also caused problems in many new vehicles, including Discovery 3s when they first came out.

So they eventually dropped the Cut-Out/Turn-Off voltage to 12.5v and this stopped most of the oscillation.

Fortunately, my isolators have never suffered with this type of problem.
24th February 2018, 06:48 PM
DiscoMick

Can I ask how lithium and lead crystal batteries compare? Advantages and disadvantages?
Possible uses would be either as a second battery or in a camper trailer.
I like the idea of getting two smaller batteries into the space needed for a single AGM, plus the weight saving.
I also like the idea of being able to discharge batteries deeper than AGMs.
What do you think?
24th February 2018, 09:40 PM
Kidbeen

Quote:

Originally Posted by drivesafe

Hi Kidbeen, the lowering of the Cut-Out/Turn-Off voltage is more to do with the Cut-In/Turn-On voltage level.

Before the introduction of variable voltage alternators, or so called "smart alternators", the Cut-In/Turn-On voltage of most isolators was 13.7v or a little higher for some.

These usually had a Cut-Out/Turn-Off voltage of around 12.7 to 12.9v

This was all good and well until alternators would some times drop below 12.7, turning the isolator off, but then not get back up to 13.7v, so the isolator would remain off.

So they dropped the Cut-In/Turn-On to around 13.2v and at first, left the Cut-Out/Turn-Off as was.

In many cases, because the Cut-In and Cut-Out voltages were now to close, this resulted in the isolator oscillating, continually turning on and off all the time you were driving.

This type of isolator oscillation also caused problems in many new vehicles, including Discovery 3s when they first came out.

So they eventually dropped the Cut-Out/Turn-Off voltage to 12.5v and this stopped most of the oscillation.

Fortunately, my isolators have never suffered with this type of problem.

Thanks for the explanation. It is so good to understand why the isolator dropped the voltage to 12.51 as I guessed there was some good reason for doing it.
24th February 2018, 10:04 PM
drivesafe

Quote:

Originally Posted by DiscoMick

I also like the idea of being able to discharge batteries deeper than AGMs.

Be very wary of this claim. If you have a 100Ah AGM and a 100Ah lithium, you have 80Ah available from both batteries.

Whereas, if you have a 100Ah Lead Crystal battery, you have 110Ah available.

The reason for the huge difference in usable capacity in Lead Crystal is because their marked rating is based on a C10 discharge rate, while nearly all other battery types are marked based on a C20 discharge rate.

The lighter load required for C20 rating, gives you more capacity, and when Lead Crystal batteries are discharged at the same C20 rating, they actually have a higher useable capacity than they are marked with.

I have no idea why they rate Lead Crystal batteries this way.

NOTE, lithium batteries are have pretty well the same useable Ah no matter what the current load is, but like AGMs, the last 20% is not available ( without damaging the battery ).

So in reality, you could replace a 100Ah AGM or lithium battery with a 70Ah Lead crystal battery and have nearly the same amount of available Ah.

Quote:

Originally Posted by DiscoMick

Possible uses would be either as a second battery or in a camper trailer.

Quote:

Originally Posted by DiscoMick

I like the idea of getting two smaller batteries into the space needed for a single AGM, plus the weight saving.

As posted above, the weight and size saving is not quite as good as it sounds.

Quote:

Originally Posted by DiscoMick

Can I ask how lithium and lead crystal batteries compare? Advantages and disadvantages?

Unless you have a major problem with weight and/or space, the vast majority of RVers, will not gain a thing by changing over to Lithiums.

But there are some situations where lithium batteries are by far the best option. These are extreme usage situations, like wanting to run an air conditioner while off-grid, or if you are cooking for large numbers of people such as a tourist camping group.

In these sorts of situations, a small lithium battery could easily power your cooking appliances for the short period of high current use at each meal and then be charged on the go between meal.

With air conditioners, there are a number of problems that need to be addressed, like needing a large combo-inverter to power the air conditioner, a large lithium battery bank to supply the power needed and then you need a means of recharging the battery bank.

Both of the above are not your typical RVers style of use.

With most RVers wanting to do just as you have posted Mick, then Lead Crystal batteries offer huge short and long term benefits over AGMs and have similar cycle rates to many lithium batteries, without the huge setup cost.

These benefits are easily gained because Lead Crystal batteries are a straight replacement for any deep cycle AGM.

On the other hand, lithium batteries have to be set up as a totally separate operation and you not only need the Lithium batteries but you also require a dedicated charging system for them.

Mick there is lots more to a comparison between Lead Crystal batteries and lithium batteries, but the above should give you the basics when trying to choose which is best for your type of usage.

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