Spektrum; DX7S( age unknown) silver face black case. Battery

[Basil]

Can anybody tell me at what is the min' charge for a Overland 2000 mah (non Lipo) pack,that is safe to use please.Also what sort of time period I might expect.  Mine charges up to 5.6 but drops rapidly to 5.3 once in use. It is new about a year ago. I was thinking about going Lipo but the battery needs to be taken out to charge. I expect comments on this subject can be quite diverse. Thanks in advance.

Bas

[GaryW]

Im running this lipo im my DX7S,,,, if you upgrade to lipo the battery chemistry needs changing in the system settings menu then you can either take it out to charge or use the Original spektrum supplied mains power supply to charge

 

Edited October 12, 2023 by GaryWebb

[GaryW]

As mentioned above when using lipo in a DX7S

Edited October 12, 2023 by GaryWebb

[Basil]

1 hour ago, GaryWebb said:

Im running this lipo im my DX7S,,,, if you upgrade to lipo the battery chemistry needs changing in the system settings menu then you can either take it out to charge or use the Original spektrum supplied mains power supply to charge

 

Gary, are you sure about charging in situ?.What do you do about the balance lead?.

Bas

[GaryW]

5 minutes ago, Basil said:

Gary, are you sure about charging in situ?.What do you do about the balance lead?.

Bas

 

Transmitter pack i use doesnt have a balance lead 

[Cuban8]

Just a quick heads up.......I don't know if Spektrum ever changed their crazy policy, but both of my DX7 trannies have the charging jack polarity reversed compared to what people might expect  i.e. they put 0V on the centre connector and +V on the outer. Obviously done to be awkward and to lock people into buying Spektrum chargers etc.

Migrating from Futaba in 2012 I wanted to continue to use my existing chargers so swapped the wiring in the trannies. Not an easy option perhaps for everyone.

Don't know if this is relevant to the existing issue but worth a mention just in case.

[Outrunner]

14 minutes ago, Cuban8 said:

Just a quick heads up.......I don't know if Spektrum ever changed their crazy policy, but both of my DX7 trannies have the charging jack polarity reversed compared to what people might expect  i.e. they put 0V on the centre connector and +V on the outer. Obviously done to be awkward and to lock people into buying Spektrum chargers etc.

Migrating from Futaba in 2012 I wanted to continue to use my existing chargers so swapped the wiring in the trannies. Not an easy option perhaps for everyone.

Don't know if this is relevant to the existing issue but worth a mention just in case.

 

I think it's a throwback from when they first started out, Spektrum used JR units, JR have thier charge lead jack plug polarity reversed to the norm.

[GaryW]

56 minutes ago, Cuban8 said:

Just a quick heads up.......I don't know if Spektrum ever changed their crazy policy, but both of my DX7 trannies have the charging jack polarity reversed compared to what people might expect  i.e. they put 0V on the centre connector and +V on the outer. Obviously done to be awkward and to lock people into buying Spektrum chargers etc.

Migrating from Futaba in 2012 I wanted to continue to use my existing chargers so swapped the wiring in the trannies. Not an easy option perhaps for everyone.

Don't know if this is relevant to the existing issue but worth a mention just in case.

 

The mains supply for my DX7S shows center pin as Positive

 

 

[GaryW]

42 minutes ago, Outrunner said:

 

I think it's a throwback from when they first started out, Spektrum used JR units, JR have thier charge lead jack plug polarity reversed to the norm.

 

One thing I did find slightly puzzling in the DX7S Manual is the part where it says the Charge port in not polarity dependant... or did I miss something there...?

 

 

[GaryW]

The 2 Spektrum Lipo offerings for the DX7S & The One I Use

 

2000 Mah = £24.99 @ Inwood Models / Nexus Modelling Supplies

4000 Mah = £78.99 @ Kings Lyn Models

4000 Mah Turnigy 2S Option = £26.99 @ Rapid RC

 

[Wookman]

7 hours ago, Basil said:

Can anybody tell me at what is the min' charge for a Overland 2000 mah (non Lipo) pack,that is safe to use please.Also what sort of time period I might expect.  Mine charges up to 5.6 but drops rapidly to 5.3 once in use. It is new about a year ago. I was thinking about going Lipo but the battery needs to be taken out to charge. I expect comments on this subject can be quite diverse. Thanks in advance.

Bas

To answer the question. A nominally 4.8 volt nimh battery is fine charging to 5.6 V. You would expect it to drop a bit at first but if it stabilises at 5.3 volts that is perfectly acceptable. Leave it on for half an hour, is it still up around 5.3 V. If it is, happy days. If it is dropping off to 4.8 V or less it could be time for a new one. If it needs replacing I would go for an 2000 mah Eneloop pack. These are bullit proof. I am still using ten year old packs in my JR 388s, always charged at 0.1C never fast charged.

[Basil]

10 hours ago, Wookman said:

To answer the question. A nominally 4.8 volt nimh battery is fine charging to 5.6 V. You would expect it to drop a bit at first but if it stabilises at 5.3 volts that is perfectly acceptable. Leave it on for half an hour, is it still up around 5.3 V. If it is, happy days. If it is dropping off to 4.8 V or less it could be time for a new one. If it needs replacing I would go for an 2000 mah Eneloop pack. These are bullit proof. I am still using ten year old packs in my JR 388s, always charged at 0.1C never fast charged.

Hi, I use the spektrum charger, assume thats OK. Leave on overnight.

Bas

[Basil]

15 hours ago, GaryWebb said:

 

Transmitter pack i use doesnt have a balance lead 

As I understand , the pack is 2s, therefore, I am told, that it would need  the extra wire to charge. Can you explain.

Bas

[Simon Chaddock]

Basil

Repeated simple charging of a 2s LiPo is likely to result in the cells becoming out of balance. It is almost impossible to build two truly identical LiPo cells. LiPo chargers must stop charging when a cell reaches 4.2 volts but without an individual dell connection the charger can only stop when for a 2s the battery reaches 8.4V. If the cells are out of ballance this will mean the cell that reaches 4.2V first will continue to get charged until the lower one catches up. Over charging a LiPo does it no good at all and can lead to a thermal runaway.

A thrid wire connected to the pack mid point allows the charger to 'see' both indiviual cell voltages however to be any use the charger must have a balance charging capability i.e cutting the charge to the full cell whilst leaving the charge on to the lower voltage one.

 

This process is avoided with NiMh cells as they can be safely overcharged a low rate until all the cells are full. A NiMh charger will drop to a suitable low charge rate once the battery reaches a cetain voltage.

 

Unless your Spektrum charger has the approrpiate 3 wire balance charging facility it will not be able to charge a 2s LiPo pack properly or tafely.  

 

I hope this helps.  

[Shaun Walsh]

3 minutes ago, Simon Chaddock said:

Basil

Repeated simple charging of a 2s LiPo is likely to result in the cells becoming out of balance. It is almost impossible to build two truly identical LiPo cells. LiPo chargers must stop charging when a cell reaches 4.2 volts but without an individual dell connection the charger can only stop when for a 2s the battery reaches 8.4V. If the cells are out of ballance this will mean the cell that reaches 4.2V first will continue to get charged until the lower one catches up. Over charging a LiPo does it no good at all and can lead to a thermal runaway.

A thrid wire connected to the pack mid point allows the charger to 'see' both indiviual cell voltages however to be any use the charger must have a balance charging capability i.e cutting the charge to the full cell whilst leaving the charge on to the lower voltage one.

 

This process is avoided with NiMh cells as they can be safely overcharged a low rate until all the cells are full. A NiMh charger will drop to a suitable low charge rate once the battery reaches a cetain voltage.

 

Unless your Spektrum charger has the approrpiate 3 wire balance charging facility it will not be able to charge a 2s LiPo pack properly or tafely.  

 

I hope this helps.  

I believe that the both the Spektrum and Turnigy batteries have built in balancing circuits and so can be charged using just 2 wires. Seems to work for mine.

[Cuban8]

18 hours ago, Outrunner said:

 

I think it's a throwback from when they first started out, Spektrum used JR units, JR have thier charge lead jack plug polarity reversed to the norm.

Interesting, I didn't know that.

[Cuban8]

18 hours ago, GaryWebb said:

 

One thing I did find slightly puzzling in the DX7S Manual is the part where it says the Charge port in not polarity dependant... or did I miss something there...?

 

 

Easy enough to do at little cost.

[Basil]

22 hours ago, Simon Chaddock said:

Basil

Repeated simple charging of a 2s LiPo is likely to result in the cells becoming out of balance. It is almost impossible to build two truly identical LiPo cells. LiPo chargers must stop charging when a cell reaches 4.2 volts but without an individual dell connection the charger can only stop when for a 2s the battery reaches 8.4V. If the cells are out of ballance this will mean the cell that reaches 4.2V first will continue to get charged until the lower one catches up. Over charging a LiPo does it no good at all and can lead to a thermal runaway.

A thrid wire connected to the pack mid point allows the charger to 'see' both indiviual cell voltages however to be any use the charger must have a balance charging capability i.e cutting the charge to the full cell whilst leaving the charge on to the lower voltage one.

 

This process is avoided with NiMh cells as they can be safely overcharged a low rate until all the cells are full. A NiMh charger will drop to a suitable low charge rate once the battery reaches a cetain voltage.

 

Unless your Spektrum charger has the approrpiate 3 wire balance charging facility it will not be able to charge a 2s LiPo pack properly or tafely.  

 

I hope this helps.  

Thats my understanding of the situation.That is why I raised this post. The replies , as you can see conflict. I will follow my basic understanding of Lipo charging re the balance lead. Sorry to say that , I was hoping for a definitive answer. Thanks Simon. 

Bas

[Simon Chaddock]

Basil

As Shaun observed a LPo battery can have a balance charging circuit built into it. This sort of features is quite common where the maximum charging input rate is set by a known charger the sort of thing typical with phones and laptops.

Obviously in a more general application you have to be sure the LiPo pack does indeed have an internal balnce charging feature and that the charger being used is within the required specification.

If these conditions can be achieved then 'two wire' charging of a two cell LiPo is perfectly acceptable. 

[Nick Cripps]

Basil,

Your original post asked about the condition of a non-lipo battery, presumably the Nimh battery that the DX7S was originally supplied with. As Wookman stated above, 5.6V hot off the charger which then drops quite quickly to around 5.2-5.3V is quite normal for a 4 cell battery of this type.

 

As far as the replacement Lipo battery that is available for the DX7S then it depends which battery you have purchased. A quick bit of googling shows that both the Spektrum replacement here and the equivalent Turnigy battery here contain built-in circuits that automatically balance the 2 cells during charging. These batteries only have a single 2-wire lead to connect to the transmitter and no separate balance lead. Both of these batteries should be charged using the transmitter's inbuilt charging circuitry.

 

Other alternatives such as that sold by 4-Max here do not contain the self-balancing circuitry and must be removed from the transmitter for charging using a suitable Lipo charger (clearly stated on the web page).

 

Whichever type of battery you choose to use in your transmitter, you MUST select the appropriate battery chemistry (Nimh or Lipo) in the settings menu on your DX7S.

[Basil]

Hello  fellow posters,!!!! After some input from Nick I bought one of those 2s Lipo battery packs for my DX7S TX. The pack includes a built in balance etc. I have been getting my Lipo's ready for some down time due to the rough weather. It has occurred to me what should I do with the Lipo just installed in my TX. Do they also need to be returned to a level for storage or stored at full charge?

Any comments. Many thanks Bas

[Simon Chaddock]

Basil

Like any LiPo you will loose some capacity and high rate discharge ability although perhaps that is not too much of a concern in a Tx if they left at full charge for more than a week. For long periods of non use a LiPo should be brought to a storage charge level preferably using such a function on a charger as it will also "balance" the cells exactly to the required voltage level. It can then be safely left for a year or more without significant degradation. 

[Shaun Walsh]

6 hours ago, Basil said:

Hello  fellow posters,!!!! After some input from Nick I bought one of those 2s Lipo battery packs for my DX7S TX. The pack includes a built in balance etc. I have been getting my Lipo's ready for some down time due to the rough weather. It has occurred to me what should I do with the Lipo just installed in my TX. Do they also need to be returned to a level for storage or stored at full charge?

Any comments. Many thanks Bas

My transmitter battery gets stored at whatever level of charge it is at when I last used it, unless it's a spare destined for long term storage in which case I will take it down to storage charge level. Not had a problem yet (touch wood). As the Tx requires a very low current it's not exactly taxing the battery and even a misused battery should power it for a reasonable amount of time.